My mom thinks my bf is a piece of shit

I'm so tired of hearing that from her :( my boyfriend really isn't, he's responsible, he takes care of me, he works full time and has good intentions for us. I'm not stupid enough to be with someone who isn't good for me. She just says that because he doesn't make thousands of dollars and drives a nice car. I was suppose to tell her I'm pregnant this weekend... but now I'm having second thoughts.. I don't know what to do anymore.