Am I being selfish or are they giving us too much responsibility at my church?

No, you are not being selfish.. If more people would volunteer then it would not be an issue. Remember the 80/20 principle. I suggest that you pick only the areas that you want to serve and say NO to the rest. It is OK to say no. Remember whatever you do, you are serving God. And he wants you to do it with joy. Don't be motivated by guilt. Trust me I have been there. Having said that, please don't stop serving, just be selective. God bless.