Anyone experience this????

Long post but I need opinions.. ...

I was supposed to get my period on Thanksgiving. I always get it early in the morning and heavily the first day it only lasts 3 days ... Yesterday at 6PM I started spotting dark red which made me think ok it's my period I'm not pregnant ( we are trying and were intimate in my ovulation window ) but it didn't last red more than an hour and has been completely brown since then but switches to dark red for like half hour now and then ... Which again it's just spotting and not a flow so I'm using panty liners.

Now my concern is this .... I have been getting positive - very faint - first response tests which even though they're faint I can see them getting darker and thicker. The lines are pink and constant so I don't think it's just the indent. But I have a polyp that bled through my WHOLE last pregnancy and my mom who is a nurse said brown is old blood not a fresh shedding of the lining - period - but I have a short cycle - only 22 days - so could it be such faint lines because even though I'm around the time of my period it's still not long enough since conception??? Or maybe my blood is an irregular period but that doesn't explain the tests or blood going from dark red to brown and barely being any there.... If I am pregnant though why would I start having such irregular blood....?

I'm so confused...... Please help. Has anyone had this happen??? If you have, what was the result of it - pregnant/not pregnant.?