Feeling fine one day and crappy the next

I'll be 17 weeks Monday. I've been lucky to not have many pregnancy symptoms, but once the second trimester hit, I started getting almost daily headaches and can't sleep well anymore. This past weekend I had tons of energy and got a lot done around the house. Felt good Monday and Tuesday and was able to go to the gym both days. No headache at all Wednesday! Then, yesterday, the headache returned, I felt dizzy and off all day, and I was so tired I fell asleep on the couch the second I got home from work. Is this normal to feel great one day and crappy the next? Woke up with a headache this morning, ugh. Not even a normal headache, just pressure in my head. Makes me feel heavy and a little dizzy.

I've been tracking my blood pressure and it's been great all week. Still experiencing some congestion so I'm wondering if that's the cause of these lingering headaches.