Wierd smell coming from my chimney that my pellet stove is connected to?

The last month or so ever once in awhile I will get a wierd smell coming from my chimney. I looked up and never saw smoke. Just a wierd burning smell. Then it would go away. I've changed pellets a couple times depending on who has them and what brand their carrying. I never noticed to see which brand is doing what. Now I came home from work and I can smell it and see some smoke coming out of it. Theres too much snow on the roof for me to go up there. What should I do? What should I look for? It was cleaned just before winter. I also burn about 1-2 bags a day.