I need to vent im so depressed

My son is 6 weeks old, i love him to death but i wish i would have waited to have him...My baby father was my boyfriend of 3 years when i got pregnant he started cheating on me constantly, i moved in with him he made me stop working so i have no money at all and was never home with me. I caught him texting girls while i was in labor, I caught him trying to see his ex the day before our gender reveal party, i still stayed. Yesterday we got in a big fight and he hit me with our son in my hand and threw our clothes out of the house. Now im 19, with a baby by myself , had to move back with my mom so me, my son and sister share one room with one bed. Im so disgusting and fat i have so many stretch marks everywhere ! Im so insecure and all i see is him entertaining girls that i used to look like when we first got together with nice bodies and no kids. I wish i could go back in time and never have a baby with him at least... the only good thing is that im in school to get my cna but who knows how long it will take to finish my classes and get a job and place. I know its my fault for depending on him i just never thought we would end up like this. I know this is all over the place i just need to get this out im so depressed.