I really want to but I’m nervous

So like I really want to start introducing anal into my sex life and my boyfriend does too, the thought of anal is very arousing and so is watching anal porn. Just from thinking about it my ass gets needy like it throbs and wants to be touched esp when he rubs his finger or dick along my hole. I really want him to stick a finger in my ass before anything serious starts but I’m just really scared/nervous/anxious that it’s gonna be gross. He asks me beforehand ‘is it alright if I put a finger in or?’ And I always say no because I don’t want anything bad to happen but I want it soooo bad. Does anyone know where I can buy an enema? And how expensive are they I don’t have lots of money, I’m broke rn actually 😅

Thank you to anyone who responds!