How to stop feeling depressed!

I'm almost 30 weeks and I'm worried about my baby ived been feeling depressed for few weeks now...not just to feel depressed but things get to me and everything I do can't seem to stop making me feel this way! I try to talk it out with someone or go for a walk to clear my mind but at the end I always end up tearing up and can't seem to stop crying...I'm worried that after I give birth It migh hit me harder...