I took 3 home pregnancy tests that were clearly positive but when I went to the doctor the next day he said their test came out inconclusive. I took another one (different brand from before) this morning and it came out positive but the line was slightly lighter this time. Does this mean I am having a miscarriage?

Did you read the tests in the time stated on the instructions? It may have been that your test was a bit more sensitive than the one used at the doctor's office.

Did you doctor suggest a blood test? That would be an option or to wait several more days and try another urine test.