Will the deception ever end

My partner and I have been doing well for so long! Its been 2.5 years since the porn stopped. About 1.5 years since he stopped attempting to look it up. I had kept very close monitoring on everything. And probably about 1 year since he's deceived me in any way. (Now I'll say that I know of, given the fact I'm pretty on the ball and pick up on the slightest vibe). Now today is my birthday and yesterday I discovered, an empty packet of performance enhancing tablets in his wardrobe. He's said they were only for us and got them off a work mate etc etc. He got them to see if they would make him last longer. Apparently they didn't work, if they did he was going to tell me about (I call BS). He's had them for just over a month. My issue is why the secret in the first place given everything we have been through about honesty. All I can see is that lying deceitful person again. I'm now back to square one. Why them, when everything was going ok?
He has been lying to me by omission for over a month. How can he do that after everything, does he just not care or is he just a sneaky compulsive lier. We normally work the same shifts in the same workplace, he's stayed on day shift, I've gone to nights, he sent me a text for my birthday this morning, I won't see him at all today and quiet frankly don't want to, I've ignored the text. I'm really thinking after all this time is it just time to say enough is enough and just walk. All I'm going to say to him is that I need some time and space at the moment. I really don't want to end it but I can't keep being hit with this.

 

Can someone please give me some perspective on this.

 

He's watched video clips and read literature to understand what it does to a person both physically and mentally to gain more understanding. He has been more loving and attentive towards me and his performance in the bedroom has improved ie is now interested in me and present. He's also stopped this jaw clicking thing he used to do unaware all the time some times more than others.
I'm not saying he's back to the porn but, he has been secretive and deceptive again, that in it's self makes me question everything however I'm 99% sure porn isn't happening.

 

He first got addicted when his ex partner wouldn't sleep with him and he got a smart phone. I have adult restrictions on his phone and forgotten the pin lol.
I have noticed on occasion it takes alot of work for him to get hard. Not that often though. It is however always manual stimulation to get him hard. It's definitely not from looking at me. I really need to investigate him further as he's not going to tell me the truth. I need to turn the house and his shed upside down. I currently check his emails,(he doesn't know) they have been clear for ages. I also check his phone bill and that is clear as well. I'll try to investigate if he has a secret phone somewhere. I'm not sure what else to do to catch him out. I did notice he kept an email advertising ipads well that got deleted.

 

Not married, we are engaged. We have been together almost 5 years. I'm really not sure why I'm staying, just easier I think at this stage, I am now seriously thinking of leaving. Trouble is we work in a small mining town away from family so I'd have to completely set myself up.