Disappearing Lines?

This morning I went to the restroom and decided to take 1 of my pregnancy tests. I waited the 3-5 minute wait and seen a positive result! I went to show my boyfriend and he seen it to, but within a minute or 2 the 2nd line disappeared. I took another test about an hour or so later, I did not eat or drink within that time, and the test came out negative. I have cramps, breast pain in right breast, have gotten sick, peeing a little more than usual, I've been really tired and sore lately, and always hungry. I am CD 24, 7DPO, and could have ovulated between the 24th-27th of August. I have included a pic of what my CM looks like as well. I am on month 7 of TTC since my miscarriage back in February and AF is due around the 11th of this month. Should I wait and test again soon, or should I just accept the fact that I may have not gotten pregnant this month? I plan to go out and buy more tests, but didn't want to schedule a doctor's appointment or due a test there until I was for sure.