What are the chances of my stomach swelling so soon?

Please see my other question if you want to know more about my pregnancy worry. I was just wondering about constipation and swelling during pregnancy. I’ve had two periods and taken two tests which came back negative but I’m still really worried. The sickness I experienced a few days after sex, I think was due to worry, however I am unsure about my stomach. I was sure I first noticed the swelling a few days after what might have been conception. A few days ago, just before and during my period, I was sure the swelling had gone down, but yesterday it got bigger again. I’ve been experiencing terrible constipation, as in I only go about twice a week, even with the aid of Fibergel and when I do go I don’t get much out. I do have IBS, however I haven’t had any trouble with it for the past year and I find it odd that it would flare up again around the same time as I had sex. I also know that stress can cause problems with the stomach, but I really don’t know. I’ve also been experiencing wind, I can feel a weird feeling in my stomach which one could describe as ‘bubbly’ and it’s been making strange noises. I have had some pains in the lower stomach, higher up than where I get period pains, and I also wouldn’t describe them as cramping. I should also mention that I experienced the swelling before the constipation although I am aware that it could then make it more swollen… Any help would be very much appreciated xxx