My ex has been extremely persistent over being best friends after our breakup. I tried, but after months i couldn't take it anymore. My feelings were still the same, and as she moved on to a new relationship, my heart was crushed. Now that she's single again, she tried to refuel our friendship. I was nice at first, but i began catching feelings and falling for her. So i asked for space and told her i was always here for her, but i was still to into her to be friends like that. (I've never been friends with an ex before) 

Flash forward to last night:

My ex came over to my house. Told me she's tired of me lying to myself. She said i didn't have feelings for her, and i only lust for her. So to prove it. She started stripping and told me to have sex with her. Cause after sex I'd know if i actually loved her or i just lust for her cause I'm single and horny and she's hot. 

I asked her that if she needed to do this to see if she had feelings for me and she said no, she only loves me as a friend and doesn't want to be with me at all. 

I told her what happens if we do this and i have feelings for her and she said "I'd respect that and give you your space" so i told her let's keep doing that. Cause sex isn't just sex with her. We've been through too much, and I'd definitely want more and want her to be with me. 

So basically i turned down sex last night, cause she thought we'd bone and I'd be like "wow I was just horny, let's be best friends" 

Tldr: 
Turned down sex with my ex, because i don't believe i could do that, or be close to her without having feelings for her. Am i the asshole for turning down a hot 22 y.o Female for sexy time because of my big heart? 