pregnancy test came out positive then slowly faded to negative ?

So I took a test and it came out positive extremely quickly in fact. I was in disbelief I had a baby boy a little over a year ago and wasn’t planning to have another for another year or so. I’m on birth control I switched from the mini pill to the combo a little over a month ago when I was at the doctor to get it switched they tested me to see if I was pregnant and that came back negative. I noticed when I tstarted my new pack no period came during my placebo week. I have an app I stay on track to take my pill everyday on the exact same time religiously I stay on top of it. Take it with me in case we are out or away from home. My husband and I do have a lot of sex and  I mean our sessions  will go on for awhile and he will cum several times in me. So I’m slightly confused as to what could cause that and if I am in fact pregnant or if it’s just a faulty test. Anyone else have this happen? I plan on taking a digital one tomorrow morning but was freaked out by this! I kept checking the test the entire night still positive and early the next morning I check and bam it’s a negative. Am I just seeing things or crazy or is the test just the one with the problem.