A diaphragm is a shallow, dome-shaped cup made of silicone. You insert the diaphragm into your vagina where it covers the cervix and keeps sperm out of the uterus. Diaphragms must be inserted correctly and used with spermicide every time you have sex.
If you're not okay with putting your fingers inside yourself, a diaphragm probably isn't for you. It's a little like putting in a tampon, though; if you can do that, you can probably manage a diaphragm.
You've got to remember to insert your diaphragm every time you have sex, so it takes a bit of self-discipline and planning.
If you're allergic to silicone or spermicide, you shouldn't use a diaphragm.
You'll be able to get pregnant as soon as you stop using the diaphragm. So protect yourself with another method right away.