Smoke coming out door

Recently bought a house with a Drolet Escape 1400-I wood burning stove (insert with blower). Our first fire failed because soot or creosote had fallen off the stainless steel liner throughout the summer and was sitting on top of the baffle and insulation. I took it all apart and cleaned the firebox all out (although i did not sweep the chimney) Since the beginning of the heating season the stove has been running perfect since the cleanout and i could leave the door wide open and not one drop of smoke came into the room. Recently smoke has been coming into the room every time we open the door and this never happened before. Could this be happening because the chimney is becoming coated with creosote or maybe so bad as being partially clogged? Or... I just happened to replace a worn door sweep on my back door which we were getting a bad draft from... Could the fact that I have closed up this draft be the cause of the smoke coming in? Its not like my house is 100% airtight, other rooms do have slight airflow coming from the edges of the window and the back door draft was made better but there is still a decent draft from the door. Or is this more common when the chimney becomes clogged (although the fire does not smother when i shut the door like it did the very first fire when the chimney was actually clogged).

And FYI because I know someone is going to yell and say I should have the chimney cleaned... I just ordered the brush and rods and will be cleaning it as soon as they arrive.

Wood was just purchased and the guy said it was seasoned for at least 2 years and it seems that it is... (its pretty light in weight and 95% of the pieces do not hiss when burning) I had run the stove continuously for most of the season so far without any pour-out and the wood always burned perfect. No matter how I open the door it pours out... It used to give a little burp if I opened too fast but then it would be fine with the door wide open but now even if i open it very very slowly as soon as its open about an inch smoke starts to come out and if i keep opening it, it just pours out more... For safely reasons I'm not even going to try and light another fire until I get it cleaned out. Recently I have insulated the basement ceiling (about 85% of the ceiling is now insulated) when I bought the house there was none. As earlier mentioned I changed the door sweep and it knocked down most of the draft coming under the door but there is still plenty of airflow (unfortunately for my heating bill) on the other 3 edges of the door. So all-in-all the house has been sealed up significantly but definitely not completely as most newer houses may be and I have been doing it slowly so I may not have noticed a problem initially if that in fact could even be the cause...

Thank you all for your prompt replies. And as i stated in the initial post I know it needed to be cleaned, was just my first fireplace/wood burning stove ever and was excited to get it going initially, and then I got the oil tank filled and decided I needed to keep the fire going to keep down on the oil bill... SO... it obviosly got put on the back burner because other things were more important but obviously now I am concerned and definitely going to put safety over the cost of heating...

I'm going to clean it out this week and re-post but in the meantime anyone who has had the same problem with any results one way or the other are appreciated so when cleaning it doesnt work I have other options...

Thanks again!

Ok... I found the problem... Pipe on the top of the stove was barely connected, there was a slight slit where the fitting enters the stove because the fitting was in at an angle. Question is, is this fitting the correct fitting to use because what holds it into the top of the stove? There is obviously the hose clamp that holds the fitting to the flex pipe but only the pressure holds the fitting into the top of the stove... Problem is that the top hole of the stove does not line up perfectly with the chimney, the stove has to sit out into the room a little for the faceplate to line up with the mounting bolt otherwise if i push the stove back further the faceplate will sit right on top of the stove with no gap and then blocks the place where the air blows out when the blower is on...

Anyway there are about 5 or 6 holes around the top plate of the stove... Is there supposed to be a fitting that is actually supposed to screw into those holes to hold the pipe secure rather than just by the pressure of the flex? (see attached picture)

Ok... But im still not comfortable with the above... The connector is sitting in the top of the stove at maybe a 10-15 degree angle and as we stoke the fire sometimes the unit rocks slightly eventually working the pipe out the top which is obviously what happened (in addition to needing the sweep the chimney) Im thinking one of these connectors would be better?? http://www.olympiachimney.com/products/cat/FF/FFCM-AC/IEL plus it seems like the tabs on the bottom would screw into the top of the stove around the hole...?