Is there something wrong with my bf....?

Please help, tonight after my boyfriend and I had sex, we layed next to each other with just the radio on not talking. He was staring into space and all of a sudden he started crying.... I finally got him to tell me why and he goes, "I'm not good enough for you." And hats all he would say. He basically pouted for an hour after that and wouldn't say anything. Then for 10 minutes he got happy all of a sudden and started joking and tickling me, then a few minutes later he started crying again.... He's broken down with my like this about 3 times now. He just stares off into space and breaks down for no reason. Could he be bipolar or something? I feel like I should tell his parents but he's told me in the past not to.... Idk what to do guys 😩 were both 17 and we've been together for a little over 4 months. Someone please give me an idea 😩