Hi hon 
I think what you're experiencing is simple anxiety. So what you need to ask yourself is *why* you are so anxious about tampons. Is it just tampons, or are you anxious about "things in your vagina" in general?
The answer to your questions about fingering and sex is: not if you are really ready, both physically and mentally.
You might want to read the following:
Ready or Not? –The Readiness Checklist
First Intercourse 101 -- for information on how to handle first intercourse, although you can apply it to other sexual activities, too!
Safe, Sound & Sexy – A Safer Sex How-To -- because if you know you're safe, you'll be a million times more relaxed
Pink Parts – Female Sexual Anatomy -- because a sound understanding of your anatomy can help with your tampon problems and general peace of mind.
In general, one thing that some women are anxious about with tampons are: will it hurt, and will it fit?
Your vagina has more than enough room for a tampon -- if you can get a baby's whole head out, you can get a tampon in -- and it won't hurt if you relax, take your time, try at the heaviest part of your menstrual flow, and know your body well.
So get some hands-on experience with your vulva and vagina and try again later when you feel more ready. In the meantime, read those artilcles and try not to be so anxious 
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Hope this helps,
--Bri