It's a very difficult and delicate thing to approach, I have a week bladder myself although I don't have a bag. I have encountered problems in relationships.
My female cousin, who's a young pretty female does have one.
I'm sure it is making you feel very insecure and my only advice to you is be honest. If it's a new relationship then there will be a time when sex will be on the cards at that point talk to your partner about your bag, why you have it and how it works, tell them so they completely understand how it effects your daily life. My cousin is fortunate to be married to a lovely man and when she was fitted with it. He kissed it and stuck a heart sticker on it ❤️️.
If your man loves you or is worthy of you then he won't care, if he bolts then he wasn't the one anyway.
As for the pain I'm assuming this is a new thing for you, don't worry my cousin said the same thing but you will get used to it. If however the pain continues go back to your doctor sweetie and get it checked.
Just remember that you are beautiful with or without the bag, it's just something extra to love and the right man will accept you just the way you are :)
what a fab, considerate answer @HughMcLuaghlin - bravo. As I get older and more mature, I know the value of looking for the person - which is how I read you answer - beauty is only skin deep needs updating - beauty is the person inside @StaceyParcella I hope you find that level of connection.