Period during pregnancy??

Hi IM's I have been spotting since 4/11 and had really tender breasts and very sore nipples, so decided to take a pregnancy test on the 9/11 and had a positive urine test. Repeated the test the next morning and got another positive. The first in 5 & 1/2 years since having my child. I have been spotting since and today noticed it getting heavier but not so much to be changing my pad. It is bright watery red now and very little clots. I did go to ED yesterday morning with a threatened miscarriage but my signs were ok and HcG levels have gone up to 2400 compare to a couple of days ago when I got a positive blood test. I'm apparently too early for a scan as they checked and couldn't find anything as yet. I cant remember my last date of when my period stopped but I'm sure it was in September. It seriously feels like I'm having a normal period with the cramps and backache. Its not painful and its bearable. My question is, is it possible to have a period during pregnancy? Am I having a miscarriage? I'm going for another checkup with GP tomorrow to see how my Hcg levels are going. Midwife a ED sent my urine away and said I might have a UTI as well.