Confused about how vaginal orgasms work/feel
In past relationships, I only had orgasms with clitoral stimulation -- not directly through intercourse. I did a LOT of research about female sexuality and orgasms and learned that I was in the majority; only a small portion of women actually have vaginal orgasms. So, I went about my life feeling contented and knowing I was normal.
Now, in my current relationship, my partner just seems to move differently/better than past lovers. Recently, I started having vaginal orgasms without any clitoral stimulation. However, they feel very different from what I'm used to. When it started to happen for the first time, I actually thought that I had to defecate! Each contraction felt prolonged and steady, and I thought maybe that just causes everything to contract -- including one's rectum and anus.
But, in the past few times that we've made love, when this sensation begins where I feel like I need to have a bowel movement, I actually get scared that that might happen there in the bed. The last time, I stopped to use the bathroom, but nothing happened. So, if I don't actually need to defecate, why does it feel like that? Is there anything I can do to keep the orgasms but get rid of that part of it? Should I move differently? Will it go away in time? Is it likely that I might actually have a bowel movement while having an orgasm?
Please help me understand this. I am really nervous and uncomfortable about this, and it actually makes me want to avoid sex.
Oh, and in case I wasn't clear, I'm talking about vaginal intercourse, not anal.