i want to be pregnant, but why is it so hard?

hello, my name is nicole.i have been with my now fiance for almost 3 years,we have been trying for a baby for almost 2 1/2 years now, ever since i was 16 1/2. And nothing has happend so far, i had one miscarriage, but that was back in ’07. I’m really starting to feel like i am doing something wrong, or that there is somethign wrong with me, you know, in the reproductive sense. But i haven’t had a normal period since about february, and in march and now april, it has just been like blood that is really light in color and the flow is just like i had scraped myself or soemthing.I’m sorry if that is too graphic, but i asked the question peole on many pregnancy sites what i should do, and they all told me to take a pregnancy test and find out if it’s pregnancy and if not, then i need to go to the doctors to get checked for std’s and reproductive health. I’m not sure what to do, but if anyone has any ideas on what this could be, please reply and i’ll tell you the rest of the symptoms, including hip pain, stomach pains, and thigh pain. I really hope that i do not have cancer or something.thank you:(