I had a similar problem when it came to being intimate with myself. Whenever I tried to m*sturbate, the youngest alter would panic and cry out. I'd usually end up giving up, or if I did climax, I'd be in tears and really upset. But then a very kind soul on this forum suggested I 'warn' my alters that I wanted to have sex with myself. I tell them all what I'm planning (not in any detail) and put out my teddy bear (away from where the action is) for the younger ones to focus on. Since that suggestion, I've been able to have one-handed good times with very little incident. It's honestly been life changing for me. I used to dread those times, but now I can orgasm and be relieved and happy (victory dancing through my home). It still takes work to reassure the alters, but wow it's worth it!

Good luck!