I fear I’ve never finished

I grew up really religious and sex negative. My therapist has encouraged me to branch out and be more confident in my sexuality. So I bought toys, cause frankly fingers aren’t doing it for me. Within the first like 10 seconds of using a bullet I squirted for the first time in my life . But like it wasn’t like “oh wow that was amazing”. And whenever I feel close it either immediately stops or like I get way too overstimulated and I have to stop or to the point I throw up and have an anxiety attack for some reason? I’m also a virgin so I’m scared when the time does happen my partner will think they didn’t perform well enough. How will I know i’ve finished. People always say “oh you will know”. But like that’s not an answer 😭