I have that on and off. Last time was a month or two ago. I'd constantly think about my T, miss him, be sad that I think of him. I would associate anything even remotely connected to him with him (i.e. the city we both live in, certain public transport that he might take, the color blue because he wears blue, basically everything around me...).

There were other instances where this happened before. I've mentioned it to my T every time it started to happen. I can't remember the conversations off the top of my head, but he was always supportive, but also didn't encourage it. The feelings would usually change with time, for example I'd get to a point where I was doing better which would correlate directly with how much I was thinking about him. I mostly think of him as somebody who can help me through hard times, so when I'm doing well I don't need him as much and therefore can do with a week of having no contact.
The last time it happened, it was a bit different because external circumstances put me into some kind of constant crisis mode. He offered to see my twice a week, which switched off missing him almost completely. I think less about him now than I ever did, even when I was doing well. I'm not sure I'd recommend this route because it sounds like it could also have the opposite effect. That's just what happened to me.
I think there's certainly lots of ways to make it less painful and intense and your T can help you with it if you talk to him about it.