Yes, he could be cheating. But before you jump to conclusions, I would get more evidence to support your belief before you accuse him of anything.
It's only been 3 months and not everyone is wired for sex all the time. This is a huge fallacy that women believe. Contrary to myth, men aren't able to have sex, all the time at any moment of the day. They suffer from fatigue, stress and emotional upsets that affect their libido. Most relationships start off with sex hot and heavy and it naturally tapers off. This is quite normal and nothing to be alarmed over. I would talk to him first, calmly, not accusatory and not angrily. Just express your concern to him in a non-confrontational manner. This won't put him on the defensive. If you still feel like something else is going on, I would do some investigating to see if you actually find anything solid to really believe he's going outside the relationship before you make any accusations. If you come up empty then you know you were way off base. If you suspect he's already cheating on you after 3 months, there's got to be other reasons to make you suspect, and it's never a good sign. Listen to your intuition. It may just be a red flag that this relationship isn't right. If there's no real evidence, you've got to start trusting in the relationship flow.
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Maybe you could romance him for a change. It doesn't have to be something physical like sex. I guess what I'm saying is this: When was the last time you did something nice and sexy for him? When guys do all the work in a relationship, sometimes it becomes a chore and we get frustrated. Making dinner or surprising him with some stimulation other than you may spark his interest again. What does he love to do? If you facilitate something he loves to do or something he wants, then he may respond in kind. Sometimes women forget that romance is a two way street and its really the little things that are the most important. Sex is nice, but sometimes we need space and enjoy things that have nothing to do with our significant others.
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