since you mention boyfriends in plural, meaning that there is a pattern, it seems that the issue is yours. Maybe this is an extreme form of being introverted. "drains me" is the language that suggests your being introverted, because extraverted people gain energy from interactions with others, while introverted people feel that interactions sap their energy.

You probably won't be able to have a traditional marriage given the high frequency of interactions within such an arrangement, but it does not seem to be the case that you are bound to live your life completely alone.

You probably need to stop thinking of it as "controlling your feelings" (which is largely unproductive and close to impossible anyway), but start thinking of this as a problem solving exercise, and, thinking along these lines, start developing flexible arrangements in which you get to spend short bursts of quality time with boyfriends, interspersed with long periods of alone time.

Also, if it is the actual contact that saps your energy, but written exchanges are OK, you can add written exchanges (and/or Skype) to your interactions with boyfriends to increase connectivity.

I do not do that kind of cardio, but I am aware of its benefits - called interval training. Alternating high intensity and low intensity periods. Apparently better than steady state cardio.

You need something like that for your life - not steady state, but intervals.