if your cycle is only 3 days away, you would only be around 2-3 ish weeks pregnant... you wouldn't feel your uterus weighed down, since your egg would just now be attaching itself to your uterine wall. brown is old blood, not implantation bleeding. I say infection. Also, if you have been having these issues for 3 weeks, that would mean they started almost as soon as your period stopped. I would go to the doctor. You could try a first response test and see, but I highly doubt it would show anything.
at 4:31 PM on Jul. 9, 2012