Check out his pupils. Are they extremely small, like a pin-top? Also, frequent scratchin & itching himself. In addition, does he sometimes have trouble getting an erection for sex?
Also if he's high he may have tons of extra energy or he'll be nodding out - basically falling asleep - if he's not doing anything. If he goes thru money like water, if he tells you he's going somewhere but isn't there or takes longer to come home than he told you. There's so many different nuances to be aware of, it's hard to name them all. Also, if he's banging it, check his arms and legs for tracks. He'll probably lie to you even if you catch him, that's what we do as addicts. And not to scare you, but if he's shooting up and sharing needles you're both at risk for HIV. Sorry to bring in the bad news but it is the reality. Good luck sweetie.
Thanks for the help guys, I really appreciate it. He doesnt have trouble getting an erection but he rarely wants to have sex and he hasnt been finishing if you know what i mean... Its been less then a month since he quit so he has marks on his arms, Its hard for me to tell if they are the same ones or if they are new though. And i have been well aware of the whole HIV thing, thank you for the concern! He has always been a bit OCD with everything being clean though so i dont think he would share his needles... well on purpose anyways... but i was already planning on getting checked soon anyways. Thanks again for the help!