HPT slightly lighter than yesterday

So I realize I'm going to seem like a crazy person...but I'm 6 weeks today and still taking daily HPTs. I had a chemical last month and that was the first time we've ever been able to get pregnant on our own (our first 2 kiddos are thanks to IVF)...so I'm just a little nervous. Anyway, I didn't think much about my test today because it was dark...but then I compared it to yesterday's and realized it was just a little bit lighter.