stomach bump? what is it?

so awhile back i thought i was pregnant because my stomach was bulging out a bit but it wasn't like i could feel an actual knot. so i went to the dr. and they said it was a muscle knot. so now its either getting bigger or i am pregnant and its just pushing it out and making the knot show worse? I'm supposed to start my period today so if i don't we'll see but i didn't think muscles knots could get bigger? i just kinda have that feeling if i am i would be maybe 2 or 3 weeks because i had my last period. but ive had this knot for probably a year so why all of a sudden would it get bigger? i didn't strain myself or anything. its kinda on one side of my stomach i just don't know what to think about it. am i worrying too much? i guess if i don't get my period then ill positively know.