I am going to STRONGLY recommend that you seek out a cranial sacral therapist. You are probably experiencing pressure and foggy feeling from a restriction in the fascia, membranes, or boney structures somewhere in your body which really can affect your brain functioning. I think you might find huge relief from this treatment technique.
The Upledger Institute
good luck with this!
Either that, or maybe it's allergies to a food or something in your environment??
Whatever it is, it's worth getting it checked out. If traditional medicine hasn't been able to give you any answers, then it's time to go through some other routes.