Some experts say if you do anal sex ‘properly, it won’t hurt. I say even if you do it correctly, the urge to say ‘Owwww! That bloody hurt!” will strike you at times.
The anal sphincter muscles are used to pushing things out, not taking things in, so you literally have to retrain your bottom.
You can only do this by taking things slowly and preparing for it properly (see How to prepare your bottom for anal intercourse).
But while it’s uncomfortable some of the time, it shouldn’t be really painful. If it is, you’ve rushed into it or you’re a bad fit (too small bottom with too big penis!)
Ironically, it will sometimes feel most uncomfortable while the penis is shallow.
That’s because it’s passing through two different sets of sphincter muscles which are determined to guard against intruders.
The external sphincter is controlled by the central nervous system, meaning you’re (kind of) in control of it.
The internal sphincter is about an inch further in and it’s controlled by the autonomic nervous system (it’s controlled by your body, not by you).
You can help relax both sets by bearing down (imagine you’re doing a big poo and push out).
Once the penis is through both sets of muscles and deeper, it should feel more comfortable.
BUT don’t rush the process to put it inside: take it slowly and while it may feel uncomfortable, it’s not unbearably painful. Barge right in and you’ll be hitting the ceiling.
Once you relax into it any pain should subside and the pleasure factor should start to kick in.