Thick white substance on BF's hand

So my boyfriend and I were having sex. We used a condom, and he pulled out before he ejaculated (like always). As he was pulling off the condom, he got some thick white substance on his hand. He said he doesn't look anything like semen, which it doesn't. I've actually seen something like it on my underwear from time to time. We inflated the condom, and it inflated fine into a balloon, and we also filled it with water and there were no leaks or spills (we even squeezed it and no water came leaking or spilling out). I'm just a little concerned. He never came in me in the condom, he pulled out before he came, and obviously there were no breaks in the condom. Could that have been pre cum that leaked out the base of the condom? My boyfriend told me precum is only a little drop. Should I be concerned? I've read that women make discharge during sex that could be thick and pure white like that. I also queefed when he pulled out, so that could have been all of my fluids and his penis making air bubbles. What do you guys think?