I'm 41 years old i've been working out for basically all my life, my
question is at what age does the body start to slow down I don't get a
pump like I used to just curious?

You said it: "I don't get a pump like I used to."  But it sounds like
you are a lot fitter that most your age.  I am sure that someone can
find a qualified answer on the web, but just as a free comment, I
remember reading that it is all downhill after 25  - but I prefer
believing that it was only after 35.  And if you keep working at it,
the slope can be lengthened.  It's not pumping iron, but I know an 82
year-old who still pulls his weight rowing 7 miles and more at a
stretch.

I read something about 25, too, but you are going to have to offer a
bit more than $2.50 to get a real answer (come on, that's not even
minimum wage).

heres the info as an ex-bodybuilder:
14-16: body growing rapidly
16-23:physical peak
23-25:physical peak may be still going strong,depends on person
25 -35:onset of signs of aging on the cardiovascular system
35+ : steady decline in performance that can be slowed by CVR
work,such as cycling,rowing.