Ok, well keep doing all your stretches to prevent anything from tightening up then but the fact its sore in the morning and loosens off does suggest things are tightening up a lot quicker than they should. Have you had your back cleared? It's all very well treating symptoms but you need to work out whats causing it to really knock it in the head. Thats where nobody on the internet is going to be able to help you as much as someone doing a face to face exam. If your physio is back next week you need to get in and see him asap, he'd want to know if its getting worse and will modify the treatment accordingly. To be honest, i don't want to start suggesting treatment methods other than simple things (I don't know you or enough about whats causing your symptoms and when someone comes in expecting a certain treatment because they heard this or that when you know its not the immediate priority for them, its a nuisance). You have your physio and i'm quite happy to give you simple advice in the mean time, but in my opinion you should be discussing needle therapy (or any other techniques that might apply) with him - as he knows your case.
So my advice (others might chip in, who knows!):
Book in to see your physio asap as you're getting worse. Avoid aggrivating activities in the mean time as if its acute inflammation, you need to give it time and space to settle. If you do aggrivate it then ice it. If any of the exercises your physio gave you are making it worse then take them out for a couple of days and see if that makes a difference. Its all about narrowing things down until you are left with the answer. If your glutes are in constant spasm it'll hurt and im sure your physio will treat that as he sees fit.