Boyfriend not interested in sex anymore

My boyfriend and I have been together for 9 months. We are both 22. We usually have sex one to three times a week. We haven’t had sex in two weeks and he doesn’t even seem to care. We spent five days apart for Thanksgiving holiday and he didn’t even seem to care about having sex before we went our separate ways. I just saw him for the first time since last Wednesday and he didn’t want to have sex. I was freshly shaven and even mentioned I had a new pair of lace panties on with crystals on it (something out of the ordinary for me) and he responded with “oh, really?” And didn’t even care to ask to see it. He had massaged my thighs and gently rubbed the outside of my vagina for like 15 seconds and then stopped and went back to carrying on like nothing happened. He didn’t even get an erection. He’s been very cuddly and loving but has absolutely zero interest in having sex with me. I’m going crazy because I need the D and I’m starting to feel depressed about this. I’m assuming the worst case scenario and I don’t know what to think.

1) what do you think is going on?

2) how do I bring this up in a non-nagging way and non-insulting way?

I am so horny and I feel unwanted sexually. This has never happened before so I don’t know what to do. He doesn’t seem actively stressed about school and he’s always talking about how tired he is but he gets 8-9 hours of sleep most nights. We don’t live together so I suppose I wouldn’t be able to verify that. Please help me ☹️