Line question

Ashleigh

So I am 3w4d as of today. I got my first bfp on Sunday night. I had a bunch of extra tests so I keep taking them. I noticed with FREP the pregnant line is fluctuating in darkness. Has this ever happened to anyone? Is it possibly a chemical pregnancy? The line is always still there but one test it’ll be darker then the next it’s light. It’s all over the place and it’s making me nervous.