Possibly cheating

My boyfriend of three years has recently been talking to my cousin who is a year older  then him her boyfriend told me that from the time he's done work until he goes to bed he talks to her I have  also notice he's been liking all her pics on Facebook I have  talked to him about this and he says he just likes her as a friend nothing more he see her as his own family but it's still bothers me I'm 31 weeks pregnant with our second child and I can't help but feel venerable. I feel like I'm not good enough for him he's always on his cell phone when we do spend time together he still has to have his phone. I love him more then anything in this world I don't wanna lose him so I keep how I'm feeling locked up because if I talk to him about this again it will probably cause a fight :(