Anyone have any advice????

I’ve been TTC for about 8 months with baby #2.

When I first stared I missed a period within the first 2 months and then everything was find the next month. Well this is the second month that I have missed my period and I’ve taken tests and they say negative. Nothing has changed with stress, or anything like that. I’m starting to feel doubtful and I don’t know what else to try.