Hi there froggie. Sorry to hear that you are experiencing some frustration and anxiety about masturbation, it's an experience that a lot of people have when they are first experimenting with what brings them pleasure, so you are certainly not alone.
I can hear you saying that you're enjoying touching your inner thighs for a bit, but fingering yourself internally not so much. This is a very common experience, a lot of people with vaginas don't really find internal stimulation all that great on its own, there are far more nerve endings (areas with more of those are more sensitive to stimulation) in other areas of your genitals, like the clitoris. To learn more about this, these articles (and then those they link off to) are a great place to start, and will be helpful to your question more generally, too:
Also, as you'll read in these articles, a lot of feeling pleasure from any kind of sexual activity, solo or partnered, has to do with how were feeling mentally at the time. Therefore if we're feeling stressed out or sad or scared, that can inhibit feelings of pleasure. Putting pressure on yourself that you "should" or "must" find what works for you asap is therefore will only make things harder, so please treat yourself with patience and kindness. It is totally fine to take a break from trying this if it is only bringing you frustration, and focus on other things that bring you pleasure and joy for the evening, or for the next little while or longer as feels right for you.
On a related note, you mention that you feel scared to touch the walls of your vaginal canal, and fear is certainly something that is very stressful. Would you feel comfortable talking about why you are fearful of this with us here? If you're having difficulty putting words to this feeling, does anything in this article particularly resonate with you? I'm scared to touch my own vagina: why?