My uBPD friend and I have been getting on extremely well this year. Since he's started to open up to me a bit more.
However a fortnight a go we hit a bit of a bumpy patch... . We'd been out on the Tuesday with friends and had a great day / fun together. So much so it almost seemed we were a couple. Then on the Friday night we went Bowling (just the two of us). Whilst we were chatting I rolled a cigarette... . At the end of the first bowling game I said I'd go up to the counter and ask them to reset the machine... . I noticed him stand up and look over as I was doing it. I came back and said it's busy, I'll go back in a minute.
Once again I went up and he stood up looking over again. I thought okay he thinks I'm going out for a fag. It was still busy so I came back... . The third time it was quiet so I went up and came back and he was sweating and said where's the toilet so I showed him and he was in there for a good 30 - 45 minutes...
I didn't make a fuss when he came out just acted normal. When we'd finish the last game he was ringing for a lift home before I'd even finished my drink or changed my shoes etc... He was in a rush and said he had to go home and study.
I went home feeling a bit miffed - I knew he didn't like me smoking but I didn't even have a cigarette. I thought I'd test the water and send him a joke message to see if he'd reply. He didn't... .
On the Sunday a group of us were meeting up. I said to my friends on the way I don't think X is happy with me - see how he acts today. He turned up late (as usual) was very off and made some nasty comments towards me. I said to my friend "see the difference from Tuesday?" She said "Yes it's funny". I'm afraid I didn't see it that way.
I jokingly called him grumpy, he said he wasn't and I said I know full well you thought I was going to go out for a fag. He smiled and said 'no I just had reading I had to do". I said "I know you by now and you're grinning, gives it away". After that he was back to normal.
I texted him that night and basically said I wouldn't disrespect him and sneak out without telling him. I asked him not to judge me on how'd been treated in the past. I ended it by saying I look forward to going out with him soon. He replied to the message and said "me too

" which was enough of an acknowledgment for me.
It's with thanks to websites such as BPD family that I have learnt so much. I was able to recognise why his behaviour went odd and address it. He obviously has some very extreme abandonment issues and believed every time I walked off I was going to walk out and not tell him.
I don't know if the staying in the loo was to teach me a lesson or to sort his head out. I'm not sure. I hope he wasn't harming himself in some way.
But as I said above I want to say thanks to a supportive website and I do believe things can improve if you know how to handle the person and the situation... . ;-)