HPT not getting darker

coralflame

My husband and I had our second IUI done on May 3rd, I had a HCG trigger shot on May 1st. My Dr told me to test at 14 days past my IUI...I of course was inpatient and tested at 10past IUI and had a positive. Had some blood work done on May 14 which was 12 days past IUI and HCG level was 21 (inconclusive) MD was unsure if it was very early pregnancy or the trigger shot still in my system. Said to test again on May 17th and if + then it is a true pregnancy.

I tested on May 17th with a FRER and got a fairly dark line (same as my profile picture) Have taken a few more test since then and the line doesn't seem to be gettig darker.

 I am scheduled for blood work Monday and Wed morning to make sure my HCG levels are rising appropriatly. I am nervous that maybe I am having a misscariage or a chemical pregnancy

Having symtoms of sore breast, slight nausea, tired and insomnia. Also been having on/off cramps for the last week which MD said is just implantation.

 My question is: Am I just driving myself crazy with repeating these test, how reliable is judging the pregnancy based on the darkness of the line?