IIN I literally can't put in a tampon?

I had the same problem! I really thought I would NEVER be able to correctly put in a tampon, but now I can.

Okay so I'm just going to give you advice and it might be TMI but here goes. LOL. It worked for me.

Wash your hands and lie down. If you've been masturbating this won't be anything new lol. Put one or two fingers inside you. Feel around inside. I know it sounds ridiculous, but if you can put two whole fingers inside (deep, trying pushing in as far as you can) you can wear a tampon. Once you've assured yourself you can do that, get the tampon and take it out of the applicator (for practice). Try inserting it with your fingers, positioning and arranging your fingers however you need. If you put the tampon in and you can still feel it, reach inside and push it in further. ALSO the tampon may be crooked (painful) so try to straighten it out. The tampon should be vertical with your body, string hanging down.
Once you've done it without the applicator, try with the applicator. Same idea. You may still need to reach in with your fingers.
The angle is very important when using a tampon. If you can still feel the tampon, like I said earlier, the angle is wrong and it's crooked.