Hi, I need advice... So I've been with my boyfriend for almost 2 years now. I used to be a complete pot head, and his little sister smoked too. I was trying to bond with his family, so his sister and I smoked together. When he asked me about it I panicked and told him that she didn't smoke. But then as he was asking me more questions the guilt kicked in and I told him the truth. We got into a huge fight because I looked him in the eyes and said she didn't at first. I swore to him that would never happen again. And it hasn't. A few months into our relationship he got tired of me smoking pot, so I quit. And now a year and a half later I had a slip up last night. I smoked. He found the evidence and asked me about it this morning... He gave me a chance to be honest and again I panicked and told him I didn't and played dumb, then told him the truth. I feel so stupid! That's what he gets so mad about (rightfully so). Is the fact that I lie before I break down and tell the truth. It's just that I don't want him to be mad at me or disappointed. And I had done sooo well! A year and a half, and I up, so that makes me feel ashamed in myself. He is so mad at me though that I'm afraid he's going to break up with me and that I couldn't deal with. This all could've been avoided if I had just told him straight up when he asked. Now I don't know what to do. He left and said he had some thinking to do... we've been through thick and thin together... I just can't believe I may have ruined us for good... please help. I need advice...

Let him cool off and deal with whatever decision he makes. Get yourself clean from pot.
Aside from that, there is nothing your can do.

I am clean, that's the thing. I hadn't smoked in a year and a half and then it was around me and I let my guard down. Aside from that we don't have any issues really in our relationship.

He Obviously does not trust you as far as pot is concerned. All you can do is wait until he makes his decision.
In the meantime stay on the right track.
I wish you well.

He will most likely never believe you stopped for year and half and will think you keep smoking behind his back,

Since you lied about it twice, he will have serious trust issues going forward.

And another major issue, if you can't tell him the truth,good or bad, there is serious communication issues.

We communicate perfectly though... really. And he knows for a fact that I was clean for a year and a half. And I can and do tell him the truth about everything, but when it came to this slip up I was embarrassed and ashamed and knew he was going to be disappointed in me... I just don't know what compelled me to do this..