Headachy and very tired

Sara
Ok so I'm slooooowly getting over a sinus infection after horrible allergies. I've been going to bed early every night, getting a full 8 hours, but this whole week I have been waking up feeling unrested, tired and headachy. My husband and I had sex 2 days in a row right after my period, so I highly doubt I'm pregnant, but who knows?! My cycles are on the shorter side- 25-28 days on average. I'm supposedly smack in the middle of my fertile window now. I'm thinking maybe it's cause I'm still not fully recovered from my sinus congestion? I know it's too early to take a PT at this point. Any thoughts?