What size boat and engine do you have? I have yet to go through the lock at Tewkesbury towards Gloucester but from my experience on the Severn so far (which isn't much) it sounds like you must have gone out on a spring tide just after the last load of heavy rain.
I went out this Friday expecting the river level at upton to still be a bit high and struggled to launch the boat... I was up to my chest in water pushing the trailer out in the marina. Didn't think I would need my waders this time!
Excellent day though, locked through to the Avon and turned around at Nafford lock. Nice river the Avon, the speed limit is a bit painful, was going a little too fast on the restart setting. But that type of boating is very relaxing and also cheap