Pregnant and lightly bleeding can this be ok?

I took a test today and it was a very faint positive. My period has been messed up since I got my Mirena out a few months ago so I didn't really know when my period was late. So for the last week or two I have been taking a test every other or every 3 days. So the test being faint doesn't concern me since it was negative only 3 days ago. The last 3 days I have been getting bleeding very light like after sex the other night i was so i just thought it was my period so I put a tampon in and called it a day the next day I wake up and take the tampon out to realize it has nothin on it. okk so i again brushed it off and went about my business and then the next 2 days today included once or twice a day I will go to the bathroom and wipe and there will be blood it will mostly be brown with a tiny bit of pink/red. I have been soo confused by it and its obviously not my period so I took the 2 tests this morning and got the positive but I just don't really know what to think of it. I have an appt with my primary care doctor 2morro and I will bring it up to him, I am also cramping but I always cramp while pregnant(this would be my 3rd) so I dont think that means too much and its not like the miscarriage I had before but I cant help but be worried and figured I would ask here to see if anyone else had light bleeding in the beginning and went on to have healthy babies. Thanks in advance for any answers = )