MelSwims

All meds contain "inactive ingredients" which may include starches & sugars, preservatives, colors, etc. What you are really asking is if those inactive ingredients are present in significant quantities to affect your fast, which is not something anyone can really tell you objectively. If you are trying to be keto and want to know if the pills break your ketosis you can buy keto strips and check yourself. If that helps. But that's kind of intense. If you just want to not eat food (= fasting) then pills are not food and you are good. 

Longtime swimmer, I concur, if you are fighting technique you will tire out. Check out total immersion swimming for some good drills to improve technique. Can also get a pull bouy and hand paddles to work upper body strength in the water, or fins with kickboard for lower body. Mix those in to regular swim laps, mix in other strokes if you can, try to go slow/medium/fast speeds for a lap at a time. For how fast to see improvements, it depends on how much you swim, how fast and far you are going and how fast and far you want to go. Beginners on a swim team go 45 min 2-3x per week and see improvement in 3-6 weeks, with appropriate drills and focus. Hope that helps!