There are many reasons why tampons may hurt...
- Lack of relaxation
The vagina is a muscular tube so if you're tense the vaginal muscles will tense, this causes vaginal walls to clench together and thus the vaginal canal narrows. If you attempt to force the tampon at this point then you'd be pushing against the vaginal walls and there will be increased friction between the dry rough tampon and vaginal walls.
Tips: When first trying tampons try after a relaxing bath, and if you struggle then rather than getting frustrated go do something calming and try again later. Try masturbating first as when aroused your vagina relaxes, lubricates, and opens so makes insertion easier. Practice tensing and relaxing vaginal muscles, then purposefully relax these during insertion.
- Wrong angle
The vaginal canal is curved, so if you were to insert the tampon angled straight up then you'd just push the tampon into the front vaginal wall rather than guiding it into the vaginal canal. If you try to force the tampon to go further when it's aimed incorrectly then this just means pushing into a vaginal wall, and thus it will cause you pain.
Tips: Try non-applicator as if the tampon hits a vaginal wall you can more easily feel which direction to guide the tampon. Aim towards the small of your back, also try different positions which can change angle of the vaginal canal.
- Insufficient flow
Tampons are dry so cause friction against the delicate vaginal tissues during insertion, this is especially so if you use rayon tampons which are more drying and rougher than other types of tampons. Without sufficient flow there's not enough lubrication between the tampon and the vaginal walls, so there is increased friction and irritation as a result.
Tips: Always use lowest tampons for your flow, and never use tampons when not menstruating or with very light bleeding such as spotting. Use lubrication with the tampon, such as KY jelly or natural oils such as coconut oil or olive oil (no Vaseline, baby oil, or lotions). Try sponge tampons which are softer and moistened before use so less friction.
- Presence of a hymen
Contrary to popular believe the hymen is not always torn when tampons are used, in most people there is enough room for a tampon to fit through the hymen and it's flexible enough to stretch, but if stubborn it may cause pain.
Tips: Get to know your genitals, look at your vulva in a mirror to see if your hymen would be an issue when it comes to inserting tampons. If your hymen is covering more of the vaginal opening then usual it can be slowly stretched with your fingers using lubrication, and if the hymen remains a problem then talk to your doctor about hymenotomy.
- Incorrect absorbency
Tampons are absorbent to absorb blood, but they also absorb vaginal moisture and thus cause damage to vaginal walls which can be uncomfortable. If using too high an absorbency it'll be more drying and irritating.
Tips: Always use lowest absorbency: if a tampon leaks within 1-2 hours it's safe to use next absorbency up, but if the tampon isn't saturated after 4-6 hours use lower absorbency or switch to pads. Opt to avoid rayon tampons like Tampax or Kotex which are rougher and more aggressively absorbent, instead look for cotton tampons.
- Allergic reaction
Rayon tampons are chemically treated, but due to laws protecting company trade secrets and lack of independent regulations there's no way to know what chemicals are used. It's possible for people to develop sensitivity or allergic reaction to ingredients in tampons, this can result in increased pain and irritation during tampon use.
Tips: Avoid rayon tampons, opt instead for hypoallergenic cotton tampons like Cottons or Maxim.
- Not inserted high enough
The first third of the vaginal canal is the most sensitive and the narrowest part of the vagina, tampons are supposed to sit just above this point and if too low they can be painful. If you feel pain as you move about or sit, as a result of the vaginal walls pushing against the hard tampon, then you know that you need to insert higher.
Tips: Make sure to insert as high as possible, during first use and if using applicator tampons it's especially common for this to occur so try non-applicator tampons and re-check instructions to ensure correct use.