You've been together for more than three years and when you go out on your own he suddenly accuses you of cheating?
I think that is a clear sign that there is a lack of trust between you. :(
When I add that to the “phases” you describe… I see red flags. :confused:
Your boyfriend has something going on inside him.
- Maybe he just needs to talk to you and get some reassurance - Maybe think things through.
- Maybe he's got deeper issues that have to be worked out - Maybe with a professional's help.
Over the three years, you should have got to know this guy and be able to make an assessment of which way he is leaning. If you think it's to the latter, talk with him about getting help. Everyone needs help every now and then.
I hope things work out for you! :)