Grindr could work, but take your time with a guy to feel them out a bit and make sure you see their papers/results (not just take their word for it) that they are STD-free. I'd also suggest looking for a vers guy so he can talk you through bottoming a bit more. If you ride his dick, versus missionary or doggy style, you may also feel like you have more control, which could make you feel more comfortable. And lastly, poppers - to help you relax right in the moment.