For migraine, it is best to try and avoid the triggers that bring it on. Therefore lifestyle modifications are very important. You can also take paracetamol tablets upto four times a day. It is more effective if take at the first sign of a migraine attack, rather than when the attack has fully set in.
There are other medications like Triptans and other painkillers, which are better avoided in pregnancy.
Chewing gum should be okay in pregnancy. Try to avoid the very sweet ones.