Can use some insight

My SO and I have been engaged for a year now and we just had our bundle of joy a month ago. Everything was going really good but lately things have not be great. We moved in together 6 months ago I have two children From previous relationship and after we moved in together he would make comments that will bother me about my kids. They got along better before we all moved under one roof. The past few weeks we have been getting into arguments something that we never did and we been together for over two years. I have been kinda giving him the silent treatment cause I am so annoyed at him and some of the things he has been doing. Just last night he said that we should go to city hall in May when his sister comes down to visit to get married. Before this bump in road I couldn't wait to marry him but we wanted to wait for the baby to be born but now I don't think we should get married anytime soon. I don't if I'm feeling this way because I'm still annoyed at him or if it's cause I really don't feel we should be getting married. What should I do? I didn't give him an answer yet and I know he will ask me about it again.