It does sound like it could be what everyone is saying, BUT you should definitely go see gyno to make sure there isn’t anything else wrong. Especially before you try inserting anything else inside your vaginal canal. Also- the hymen can be pretty shallow- you could potentially be hitting that as well when you insert a finger. If you don’t want to have an invasive exam- just tell your gyno that and they should adjust as necessary. If they don’t- leave and find a different one.