It depends when you are measuring. Usually for a day or so after a PE session it will suffer from smaller erections and, although I don’t know the science part, it’s mainly due to your penis being in repair mode due to the internal damage caused by the PE (although this is a good thing, same as muscle building, it should come back bigger and stronger.)
To get an accurate reading you should measure after a two day rest with no PE at all. So assuming you PE Monday to Friday make your measurement night a Sunday. However, I add the caveat that you shouldn’t measure too often, otherwise you’ll just get disheartened if it seems to take too long.
If you are measuring after a break, it could mean you are doing something wrong. For a start, you seem to be doing a lot of serious girth work. Horse 440s are particularly extreme and being a relative newbie you should maybe take it easy with the intense stuff for a couple of months or so. The other thing that it may be is that seeing as you are doing all these intense girth exercises your cock may have traded some length for girth. When I first started on my girth routine I lost 1/4” length, but gained 1/4” girth.
Thats it for now. The most important thing is to listen to your cock, if it’s having trouble ease off or give it a rest.
LB