I Have Been Having Many Digestive Issues For A Few

I have been having many digestive issues for a few years now... Including weight gain, stomach pain, constipation, very slow digestion, muscle aches, fatigue, headaches, excessive bloating, and some others I can't think of right now... I have been diagnosed with has humorous thyroid iris and hypothyroidism and am treated for it... My tests are all normal now... Also I was tested for celiacs disease and I was negative for that... I know I am lactose intolerant and have bad acid reflux so I don't eat any of those things.... Despite having no vitamin deficiencies and good blood tests and eliminating acid foods and dairy,,, I still have all these symptoms and I need some help on what it could be