Cramping and spotting?

After 6 mths of giving birth, I started having cramping which hasnt gone away now 3 mths later. It doesnt go away like ovulation or period-is-coming cramping does. Im feeding so my period hasnt came yet. I came back on the 5th from being in Slovakia w/ my hubby's fam for a mth & while I was there I didnt take my bc pill. Last week had 2 days of brownish spotting. Thought I had my period but it never came. Now Im having stronger cramping. I talked to a nurse who said I needed to get checked out for the cramping & now also pregnancy. I went to the dr today who treated me like I was crazy. She kept saying how its normal for my period not to come yet which I knew & wasnt there for & I told her that! She took a urine preg test that came out neg. I asked for a blood test cause a urine test wouldnt come back true w/ it only have been 2 wks. Other than that she did nother! So needless to say Im mad & not sure what to do. Has anyone had cramping like this? What do you suggest I do?