My bf and i usually use condoms but today we ran out and we had sex unprotected and after a while he made me stop and then his penis pulsed (like the flex thing guys do) so i pulled out after the second pulse but  no fluid came out until like 5 mins later. But the thing is he didnt flex his penis and he said he felt it flex as well and he's not sure if he came, but so is it normal for penis to flex without the dude flexing and it not being cum?