Late or just too fat???

I've never been one to keep track of my periods. They always just seemed to come around the same time every month, so it was never a big deal. However, since getting married in December, I started tracking my period/assumed ovulation to try and concieve. I have 2 children already, ages 8 & 5 and just turned 30. I think I am 3 days late on my period. I was late last month by 3 days, but got my period around 8pm on the 3rd day. So far, no bleeding, I am trying so hard not to get excited. I used one of the graphs on here, to figure out my cycle lengths, and they seem to vary just about every month, so I guess I really don't know how late I am?? Also, just wanted to ask, for those overweight. I got pregnant with my first 2 overweight, but still "healthy". I am now heavier than I've ever been (even after I gave birth). How much does weight really factor in?? *sigh* I just wish I would know, pregnant, not pregnant, and trying to be patient.