Help!! Tampons!!!

I'm 17 years old, I've been having my period for 4 years now and I've never used a tampon before. My hymen is still intact, will I hurt myself if I try to insert a tampon because my vaginal opening is too small for a tampon to fit. I have a phobia of anything going inside my vaginal opening! How do I cope up with this? I just don't wanna hurt myself and I really need to wear a tampon as I HAVE TO go for swimming on my period days :(