At this age sometimes any attention is better than no attention-even negative attention. It's possible he's at an age where he is trying to find his niche in the family and may be feeling like "odd man out" even if it is untrue. Can you maybe spend more one on one time with him without boyfriend and sister around. I know with my girls sometimes I would just toss one of them in the car and go the few miles to the store and maybe get a candy bar or pop and drive around a little-no distractions and no interruptions-by doing that he can't escape and you might be able to get a better handle on where his head is at.
I can remember driving around with Hope my stepdaughter, she was about your son's age and was acting out, I threw her in the car and over the course of our conversation, out of no where she said "you know Alice, it's pretty sad when you find out your mom is nothing but a whore" WOW!! I was lucky we didn't wreck, but it opened the door for her to let me know where her head was at and we were able to talk through her feelings. YOu just never know what a car ride will reveal.
Good luck I know it's hard. Alice
Julia-23,Hope-22,Jennifer-21,JD- 5 Yes I am crazy.
Hope is the thing with feathers that perches in the soul and sings the tune without the words and never stops at all.