Help! My son is aggressive towards me and Im 35 wks prego!

[longmountainart]

My 5 year old son has been very aggressive towards me especially the last few months. He has been going through a lot lately and I know that is the reason for this, however the aggression is only towards me and im 35 weeks pregnant. Long story short; My hubbys brother has always lived with us because of a medical problem. My son is very close with his uncle who has currently been out of state waiting for a new liver for the last 2 months. there was a two week period where dad was gone to stay with him there. Those two weeks were sooo bad for us. We fought constantly, he was trying to hit me and hurt me and having meltdowns about everything. When dad came back things got better however the last few weeks they have been getting bad again and tonight he slammed the freezer door into my head because he already had his dessert and wanted the ice cream i was having. i grabbed him and shouted at him, which i know was a really bad reaction on my part but i was frustrated because i was fighting with him over this stupid thing. he doesnt fight with dad about stuff just with me and i am feeling really sad about it because our relationship is really starting to go sour. he doesnt want me to put him to bed or always wants dad to do things not me. i dont have a close relationship with my own parents and really want to have a authentic relationship with my children. usually i have a lot of patience with him when he has his meltdowns but is it really normal for a five year old to still have so many temper tantrums? im getting really nervous about the coming birth of our second child and i want us to be a close knit family but it feels like its falling apart. im not getting too much support or many suggestions from dh besides him telling me to have a talk with him...which ive done but he doesnt know how to express himself very well. i need to find a way to reconnect with him and im not sure how do to it. We spend all weekend together alone since dad works 12 hrs on the weekends. has anyone else had to deal with an aggressive child while pregnant or does anyone have any ideas how to reattach to a young child? help please!