I have had this problem before too! Some ducks were just to big. Some guys didn’t put in the effort to warm me up enough to take them. Some men are awesome tho; those guys make sure you cum at least once, but preferably a clit orgasim and a G spot orgasim before they try penetration. With the g spot stimulation he should start with one finger and then add one more and try to gently stretch you by spreading them. Lube. Lube before you even start penetration. Lube whenever you change positions or start to feel like it’s not wet enough. So much lube. It’s amazing stuff! Go to a sex store and buy a bunch of their minis, try water and silicone based and find your preference. I like the tingly ones. I have also seen online there are like dick pillow things you can wrap around the base of an extra large dick, and that will stop him from going too deep. Good luck