The first and most important thing is for you to feel safe and comfortable in your own skin. For most of us, that part is an ongoing journey.
Look at it this way...if you can't be completely honest with yourself and the others in your life then you would be setting yourself up for some serious drama and heartache.
I think you might want to at least consider discussing this with your boyfriend first. If he is truly mono and possessive, then there are going to be some very unpleasant times ahead for you. Wouldn't it be better to start this relationship out being 100% yourself and honest about it than to have issues down the road?
Also, it seems like things are moving at a pace that is uncomfortable for you with your boyfriend. Him moving in with you when you have lived far away from each other may not be a good plan. Maybe you could suggest that he get his own place first so that the pressures of developing the relationship won't be so high. ---As you do some reading here, you will find that it is often strongly advised not to jump into moving in together, particularly in a just budding relationship that has been previously maintained long distance.
Wishing you the very best.