I Am A 44 Yr Old Woman Who Has Bipolar

I am a 44 yr old woman who has bipolar I currently take 100 mg of Neurontin bid, 200 mg of Lamictal bid, 5 mg of Valium bid and have been taking Doxycycline Hyclate for the past 9 days for Strep throat. Yesterday and today I started to feel dizzy and tired about 15 - 20 min after I have eaten. I got so busy at work that I didn't get ahold of my primary Dr and just tried to call Wallgreens and the pharmacy is closed. Could this be a medication reaction or something more serious? Thank you