Hi Izzy
I'm sorry to hear you are experiencing this. I have what seems like the same issue. I have no sensation whatsoever of the need to pee, then I experience a cramping or pain and either simultaneously or a few seconds later, I start to pee. My bladder completely empties and I cannot stop the flow.
I have overactive bladder, and other health conditions including fibromyalgia, connective tissue disorder and an autonomic nervous system condition.
I was diagnosed with overactive bladder a few years before this specific symptom started. I leak small amounts of urine throughout the day and when I have the urge to pass urine I can only hold on for very little time so frequently wet myself, anything from a small leak to the full bladder.
When this spasm symptom started, I was having other gynae problems too with extremely heavy periods, and I had suspected endometriosis. This wasn't the only reason endometriosis was suspected - I also had other symptoms of that - but the GP suspected that the endometriosis had grown around the bladder or through the bladder and was causing the spasms. However, this was found not to be the cause because when I later had surgery (partly for something else) they didn't find any endometriosis. My periods are now less bad than they were but I still have this spasming problem, independently of that.
I've now been told that my bladder problems including the spasming are overactive bladder, partly due to weak muscle control because of my connective tissue disorder, partly due to neurological problems. The wrong messages are being sent between my brain and my muscles, which is causing muscle cramps and spasms, and this affects my bladder (as well as other muscles in my body). So my bladder spasms and empties at inappropriate times.
So I guess the short answer is that yes it sounds to me as if this could be part of overactive bladder. I don't know if this could be caused by a UTI. I have been fortunate never to have experienced this except for once many years ago (and many years before the spasms started). So I'd say spasms can happen in the absence of a UTI. Saying that, I know UTIs can cause extreme urgency and bladder pain.
It could be worth getting an appointment sooner if you can, if you are worried about a UTI, as that can often be treated quickly with antibiotics. But I know how hard it can be to get a GP appointment. Possibly could you ask your surgery if you can drop a urine sample in and they may be able to get it tested without you having an appointment? I think that can be possible.
I take an overactive bladder medication which helps a little bit, but not much. I think it helped more when I first started taking it about 8 years ago, than it does now. My other health conditions that are contributing have deteriorated, so that probably makes sense.
By the way, I don't want to worry you - I'm not suggesting that you are likely to have any of the other health conditions that I have. There are lots of reasons people have overactive bladder other than these conditions, and I know it's especially common after having children. There are different medications available and I think it's really worth seeing the GP, if only to get referred to get an understanding of what is happening.
In the meantime, have you been able to find pads that work to offer the right protection when you do have accidents? For me using the right protection, which I order online as it's better and cheaper too, helps a lot in my quality of life and not being anxious and embarrassed about accidents.
xx