Very big penis Vs. Small vagina

Hello girls!

This is my first post here on eve, I'm almost 19 and I'm Italian.

I've been having lots and lots of awesome sex ever since I lost my virginity at 16. I'd think I'm fairly experienced in the field. But right now, I'm facing a problem: my newest fuck buddy has a 9 inch dick.

He's my fourth male partner, but the other guys were all around 6 inches, I'm not really used to that kind of length...

The sex is fantastic, the only issue is that I feel very sore afterwards, so sore that it hurts to pee and wipe for a few hours. There's no blood thankfully, it just burns a lot, which is a real bummer because with other partners I was able to have sex marathons with multiple rounds, and with him I just can't. And of course I can't even masturbate the day after, which is frustrating as hell.

So, does anybody here have any advice? I don't have lubrication issues, but should I still use lube? By the way, I'm on bc, so we don't use condoms (we're both clean, no worries).

Do you know how I can relax my muscles down there, besides doing lots of foreplay of course?

Thanks in advance :)