Hi there gals. I need advice.

I have a low tolerance for heat, am kind of out of shape (though now that it's nice out I'm trying to go on walks and stuff when I can bring myself to), and am on several meds for ADHD/anxiety/depression which can have an even greater effect on those things (tolerance to heat and exercise) not going well for me. Like I want to get to the point where these things are not a big deal for my body but realistically it's not going to happen very quickly.

My boyfriend loves adventuring which means going to shows, going to parks, going to festivals and outdoor events. Biking and walking medium/"long" (in my perspective) distances to those events and back. And I like to do those things sometimes but my limits are not as big as his are.

Yesterday I made myself very sick from walking around in the heat past my limits to keep up with him and it made me realize I have to speak up about when I need to sit or slow down or find somewhere cooler to be for a bit. My problem is that I don't want to disappoint or upset him and after having a serious conversation about it I feel like I have. That I suck, I failed, I'm a burden.

He just likes to keep going, doesn't like hearing any complaining, and is a lot better with handling physical things outdoors in heat than me. I understand we're different.

I am just wondering if anyone else has dealt with a similar thing?

And if so, how to compromise or explain something like this without feeling like you're wrong? Or inferior?