Unable to conceive except once when I miscarried early. Why is this happening?

Hello doctor,

I am 25 years old. I am healthy, no medications, regular periods of 28 to 30 days. My partner and I have been together for seven years and we have been TTC for five years with no luck. I have given up hope for a long time. End last year, I started seeing a chiropractor because of lower back pain. Early this year, my period was a week late and I felt different. So, I decided to take a pregnancy test. I had two positive digital tests and another positive on the first response with two lines that appeared. I was definitely pregnant. I could not believe it! The only thing I had done differently was to see a chiropractor and it was instant that I conceived. Unfortunately, I had a very early miscarriage. Just two days after my positive tests, I began to bleed and confirmed with a doctor it had been miscarried. To this day, I still see a chiropractor and we keep on trying to get pregnant but it is not happening. I am back to feeling hopeless. I still cannot believe I saw three positive tests. I thought I would never see that for myself. I was so close. It gives me the slightest hope that maybe it will happen for me one day. Is there any information you can give me? Why is this happening to me? What might help me?