I've always been jumpy, so I can't help you there, but I can relate to your question regarding bloating and weight gain.
We got married in April and so we were happy and ate and got heavier. A lot of my work clothes weren't fitting. I am currently between 5 and 6 weeks and have what could be construed as a pregnant belly . .. but we aren't telling anyone about it until after the holidays - when we are closer to 3 months.
I keep reading things about maternity wear, belly bands and "inbetween" clothes for after giving birth . . . I really don't want to but 2 whole new wardrobes. May just live in yoga pants . . .
I can't answer re the jumpiness part, but UT might be better to get in between clothes right now and pick up some maternity clothes later.
Re having to buy a maternity wardrobe, it's totally worth it IMO. You'll need the inbetween clothes for a few months, then the maternity clothes for the rest of pregnancy and a month or so after baby, and then the inbetween clothes for a little bit again. It's nice to have some nice maternity wear, it's more comfortable and there's something about dressing well that keeps you feeling up.
Since I found out that I am pregnant I have noticed that I have been a lot more jumpy or easily startled. Before I found out I was not easily startled by anything but have noticed that I am a lot more jumpy now.