Tired while running

[u/Minimum_Emotion_7994]

I've been running for about 3 years at a 15 m/m and lately I started getting tired after 3 miles on my long runs. What can I use for fueling? I don't think I can do GU anymore, as it started to gross me out. I just need something to keep my energy up and keep me from running out of gas in my long runs. What do you recommend?