Can't tell if weight gain has slowed me down?

Your problem was mentioned and it's not necessarily the weight. It's your lack of speed. Start getting your fast twitchies to fire more and become a better athlete. A better athlete is a better runner. Without speed, you can not reach your potential. All the top international athletes these days have good speed and leg turnover at the very least.

Yeah, I need to work on speed. Compared to my teammates I'm not great at distances less than 400. Also not strong at super long distances either. But it's 200m repeats that make me realize that my legs just don't move. I have a good kick at the end of the 1500m, but it's these shorter distances that I can't seem to hack.

You have an unhealthy relationship with food, eating, weight and running. That combination has destroyed lives. No one should be giving you advice on this but your doctor and/or therapist.

I agree with this suggestion that proper diet and weight management will have a great role in your life. It is better to follow the advice of a dietician than to disregard it. You will always see a noticeable change in your running life.