Short version: Swimming is still mostly feeling good, and help is on the way.
I still feel uninjured as I continue to try to build back into swimming regularly. I was thwarted early this week, however, by the, shall we say, inconsistent climate and temperature control in our aquatic center. At last Monday morning's 5:30 a.m. practice, the temperature inside the facility was not much warmer than outside, and sadly the water was cold too. I tried swimming anyway (I got my ass up, after all!), but after 1000 yards, I was not loosening up, and my shoulder and hamstring were feeling tight, so I called it in. When I went to the pool Tuesday evening, the water temperature had fallen by a degree, and given how things had gone Monday morning, I went home without swimming. But Wednesday's strength-training was rigorous, and Thursday evening I had a good swim. Saturday morning I had a great swim, clocking 2100 meters and even being able to do a set of 5 x 50 BA/BR descend at the end. It was at about 1500 meters that I started feeling really good--really loose and strong--and I took that as a good sign, because that is about when I used to start feeling good when I was swimming healthy.
I also managed to get in to see my physical therapist on Thursday (took some finagling to get past a receptionist hell-bent on requiring a referral, but I guess it pays to know people). He did quite a series of diagnostic tests, and even had another therapist do the same, and they agreed that the problem with my hamstring seems to be coming from tightness in the muscles of my hamstrings, hip flexors, and lower back. He has given me some stretching to do at home, and also some ab work, and when I get back from traveling this week, I'll have some regular appointments with him to work more intensively. I found that having gotten some expert opinion on this also made me feel more comfortable in the water: he said that he thought the problem may come most intensely from the way I hold my body when swimming, so I tried modifying position here and there, and I could see that that seemed right. I know, for instance, that kicking with a kickboard may make things worse, so now I do not do that.
This week's workouts will be disrupted by travel, and I even bailed on this morning's practice to save energy for the work I need to do while traveling. But I am hopeful.