What Causes Anemia, Hypothyroidism And Gastrointestinal Discomfort?

I m a 29 year old male and I normally run 70-80 miles per week. The past 5-6 months I have had decreased running performance and have been struggling to handle this level of training that I normally can handle with ease. It takes much longer to recover from workouts and I can t handle the same level of intensity of training I could before. I m concerned about possible underlying issues that could be contributing to this, including anemia, hypothyroidism, or low testosterone levels. I also have been experiencing some GI discomfort after intense workouts, and I have a family history of Crohn s disease, so I m also concerned that something like this could be the issue. I m not sure what type of doctor I should see (sports doctor, GI specialist, endocrine??) or how I should go about ruling out some of these issues. Any advice or help would be appreciated.