Stomach Pains

Lately on all of my runs, I have been getting an intense stomach pain. I have been running at a slow pace, so I am not going too fast and before I run I have been eating toast, eggs, yogurt, and granola. The pain usually gets pretty bad which forces me to stop, and if I don’t stop it just gets worse. It usually goes away within 30 minutes. I used to run in high school (for reference I am a senior in college) and I never got this, and last year I trained for a half marathon and never got this either. It only started when I started training again for my upcoming half marathon. Any advice or help would be great, thanks!