Another question. Sorry

Sorry about the major influx of questions guys.. But better safe than sorry right? Today I finally set up and used my infrared lamp. Yay! When I was done I felt like I needed a victory fap, so I did. One thing I noticed was that during the time I was masturbating, my eq was changig. At first I was really firm and longer than ever, but after a minute or two my penis was only 4.5 in long. Normally I am 5 to 5.25 on a good day. Is this normal? I’ve never masturbated right after jelqing so I don’t know.. Thanks!