He is not into it

So, I've been dating my boyfriend (I'll call him "K") for about 6 months. And in the past month our sex life has pretty much declined to nothing. We never had a ton of sex, but we used to have it about once a week. Most of the time, we'd prefer oral sex because it helps me orgasm easier. But lately we haven't engaged in any sexual activity at all. He'll help me get off by fingering me or using a vibrator on me if I ask. But we no longer have intercourse or perform oral sex for each other. And I like performing oral sex on him, and I offer to do it. But he claims to just never be in the mood. I'm not sure if I'm the problem; I have put on a little weight, maybe I'm not as attractive? Or could it be that he's overworked and tired and his libido is gone? Or is it something else? Or someone else? I don't think he's cheating on me, but I guess one can never really know. Any advice, ideas or help?

The answer to your issue is to ask him. You need to discuss it with him to find the reason. You will then start the process of having communication about the lack of intimacy in your relationship...two very important factors in any successful relationship.