maybe I'm being crazy

To start: I have a 6 month old & I am not on birth control. Anyways, my husband and I had sex on Sunday, so not even a week ago. I know it's way way too early for pregnancy symptoms BUT just since yesterday I have been having light cramps, tender boobs, a horrible horrible lower back ache, and I feel exhausted literally like I haven't slept for a week straight. (Mind you my period shouldn't be here until the end of May) maybe I'm getting early period symptoms? Idk. I don't remember this with my son. And I know it's way too early but I don't know why I feel like this!