Devastated

Hey ladies sorry in advance for the rant... I have been trying to conceive since October when I had an early/missed miscarriage. 6 months before This I had a D&C at 19 weeks as my baby had a major heart defect which was really devastating and has probably scarred me for life. First forward last month we did everything to try and conceive so we could have a 2020 baby and a miracle after everything we have been through. I got a faint positive on first response at 9dpo, but then got no second line at 10dpo and another very faint line at 11 dpo. At 12dpo in the morning I got a clear positive and the line was darker which I was excited about. I posted a pic of the test on here and everyone could see the line. Today at 13dpo there's no line. I'm so confused as to what is going on with my body. I thought lines were meant to get darker every day or every other day, not dark, then no line, then faint, then dark, then no line again a day before my period is due. It's an absolute mind fuck and it's really devastating because I got my hopes up only to get knocked down again. Is there something wrong? Is it a chemical? I'm confused and pretty down about it all.