Stomach issues after eating for 2+ weeks, what is going on?

For the past 3-4 years I have struggled with undiagnosed stomach issues. Originally it was thought that they were caused by my period and whatever undiagnosed mess was happening with that, but I haven't had my period for over a year (hormone blockers) and the issues remain and seem to be worsening. About a year and a half ago my doctor said it was lactose intolerance but I have discovered that, although cutting lactose from my diet helps, I still have the same symptoms with other foods. In the past year the issues have gotten decidely worse with frequent horrible cramps, bloating, fatigue, gassiness, acid reflux and heartburn, and nausea. I recently got a referral to talk to a gastroenterlogist, but it will be a bit before I go in and see them. There is generally not an extended period of time (more than a day) in which I have no stomach issues or body aches. Recently I noticed that IMMEDIATELY after eating these symptoms flare up for atleast an hour or two.

I also struggle with wide spread undiagnosed muscle problems, chronic fatigue, an autism spectrum disorder, other mental issues, and lightheaded/dizzy spells that make me need to lie down. 

Any ideas as to what on earth is going on with my body?

congragulations! you have developed a chronic condition called GERD!

Your symptoms may be IBS if you have change of bowel habit as well.  You can also get joint pain with IBS which can make your periods worse.  Try a food diary.  I would also come off the hormone blockers which are not good for you.  They may be contributing to your symptoms. 

Fibromyalgia can also cause dizzy spells, fatigue and joint and muscle aches.  IBS can also go along with it.  I have IBS and Asperger Syndrome too.