Hi Mamaof6,
Welcome to the forum! I'm so sorry to hear everything that you've been through. I've had absence (petit mal), complex partial, and simple partial seizures for 35 yrs. I also had 2 brain surgeries to help reduce my seizures.
The tumor could be causing your seizures not to mention hormones changing each month. If you haven't started doing this get a calendar and write down what time you have any seizures along with a discription of the seizure. Also take note when you start and stop your period. By doing this you may see a pattern as to what time of day/night or what days of the month you are more likely to have any seizures. I always have 2-3 days of seizures when the hormones are changing in my body right before my period and then again after my period.
Try taking vitamin B12 1000 mcg. I have found that this vitamin helps calm the nerves down and has reduced my seizures.
The nervous feeling you are getting in your stomach is known as a aura seizure the moment this starts try tightening up all the muscles in your body and make your hands into tight fists by doing this it may stop the seizure. My neuro. taught me this back in the 1970's. Stay away from nutra sweet ex. diet soda, it's been proven that nutra sweet causes more electrical activity in the brain and can cause seizures. You might want to try going on the ketogenic diet to help stop your seizures. The diet has been out since 1927 and it works great stopping seizures. I have a cousin that had grand mal seizures and was on the diet during WWII and he flew airplanes and never had a single seizure until he went off the diet.
Check out these websites for more info.

www.epilepsy.com

http://www.neuropat.dote.hu/neurology.htm
When the main page comes up click on epilepsy

Here's wishing you the best of luck and May God Bless You!

Sue