Trouble talking

My boyfriend and I started dating February 26th of this year and he has depression and stuff like me, and he was really stressed so we broke up around the beginning of May. And on June 16th we ended up hanging out and shit with all our friends and later that day at 2 am. He texted me saying he missed me and that he really missed me and that he fucked up. And now we're back together. But on May 30th my mom died from heroine overdose and I've been in mourning. So now I'm always upset and insecure. But it's hard to talk to my boyfriend about stuff. And when we're hanging out with friends he always talks about how when we were apart he was with tons of girls. And it bothers me and he talks about his ex's sometimes when he's around his friends. And he doesn't really pay attention to me when they're around. He used to ignore me when we first started dating but he's been getting better. I just really wanna be able to talk to him and trust him. And I love him with all of my heart. And he called me on the phone crying when he was begging for me back. I'm just lost and I need advice.