Condom Question

This is kind of a strange question, but here goes.

I have never really needed to use condoms before, but find myself needing to use them as my new partner requires that I wear one as a birth control device. My problem with using them is that I put out so much pre-cum that they start getting kind of loose down the shaft and I’m afraid that because of this, it might slip off inside my partner and cause a disaster. In the past, before PE and the information on TP, I thought it was because I was just too small compared to most, but after reading info on this site, I feel that my size is pretty normal and that most condoms should fit me. I’m currently 6 5/8” EBP x 5 1/8” EG.

I bought a package of durex brand and it seemed to fit nice and snug. It had a resovior tip, so I didn’t leave any extra room other than that at the tip. I rolled it down my erect shaft as far as I could get it to go which was about a 1/2” from the base of my dick. To simulate sex, I put some astro glide on the outside and put the porno on. I used my OK grip to simulate having sex and at first all seemed fine, but after about 10 minutes, same old problem - a lot of liquid trapped between the condom and my shaft causing it to want to slide up and down my shaft.

Is this normal? Is there anyway to combat this short of stopping and putting on a fresh condom? Should I be using a different brand or size?