First Signal

I've had positives on the Walmart tests (First Signal) since Sunday at 10dpo. The tests have been faint, but getting darker. I've photographed at the 10 minute mark and then after about an hour. Today's test was darker at the 10 minute mark but dried lighter. Should I be worried? I've lost 3 in the past year. I don't go for a beta until tomorrow. This pic is the 10 minute mark. Bottom test is this morning.