Positive PT but then period

I’ve been trying to conceive for over a year now and twice in the past three months my period has been a day late, so I’ll take a test and it’s positive only to then get my period within hours or a day later. Then my period only lasts for about two days as opposed to my normal 4. I’m assuming this is a chemical pregnancy? Has anyone had this happen? I’m almost 37 and have two children already. I think it may be my age. I’m healthy and very active. I haven’t made a dr appointment yet, but think I may. Thanks for listening!