My lower back/sides gave out yesterday, still hurting

YANMD. Yesterday, the oddest thing happened—my lower back all of a sudden “bunched over” and my stomach felt incredibly heavy, every little movement hurt (spasm-like feel on the lower back and lower sides). Called my doctor, got a RX, but it’s still not helping.

This happened yesterday while I was doing #2. During a push (which was normal, not straining at all), all of a sudden, my back just kind of “bunched” over (hard to explain, but that’s the best term I can think of). Getting up hurt; my stomach and back both felt heavy, and I had trouble breathing. I put ice on my back, called my doctor, got a same-day appointment, got looked over, got prescribed Cyclobenzaprine (flexeril), and went home. Felt somewhat better, but the pain was still pretty intense, especially when moving or shifting at all. Kind of spasm-like/stiff/painful, if that makes sense. Very annoying. I took the Flexeril as prescribed before bedtime, and it didn’t really help. Took another pill this morning, still didn’t help much. I have ordered a heating pad and will try exercising a bit, as instructed by the doctor.

My doctor performed tests for kidney stones (x-ray and urine), nothing. He suggested I might have somehow put pressure on my back when carrying a bag of somewhat heavy groceries on Monday for ~30 minutes, and this triggered some kind of lower back/side pain. It was completely unexpected because my back was perfectly fine, right before that fateful #2 push, then boom, continued pain.

I’m concerned because discussions online say Flexeril is supposed to sedate you and help relax your muscles. Unfortunately, that’s not really the case for me; other than feeling somewhat more relaxed, my muscles are still very tight and stiff. I have to support myself when I get up or get down, otherwise my lower back/sides kind of “scream” or “tighten”, for lack of better terms. It’s really kind of scary, and I feel immobile. It’s especially hard because I’m single and live alone, so don’t have a support system, on top of being Deaf. I’m scared that I’ve somehow entered a nightmare and won’t ever get better (although logically I know that’s probably not true).

My questions:
1) Again, YANMD, but what could be going on? I find it hard to believe a simple carrying of something a bit heavy could trigger this (especially as I’ve done it many times before). I did suspect initially kidney stones, but that was ruled out by tests.
2) For those of you who took Flexeril before, did it not kick in and work the first couple of days? Is this normal?
3) This morning, when getting out of bed, it hurt pretty badly to get out of bed (no items nearby to hold on/support me getting up). When laying on my couch, however, I have items to hold on and reach out to, which helps me get up with less pain. Given that, should I sleep on my couch instead of my bed, for the next days until this hopefully goes away?
4) Anything else I should know — have anyone here experienced similarly before, and how did you get through it/heal? I really am hoping this is a temporary, short thing (~1 week), not a long-term thing.
5) If the Flexeril does not work at all within the week, and I still am experiencing this acute pain, are there any specific keywords or ailments that I should mention to my doctor, to check for?

Thank you, this is so frustrating and came on so suddenly and unexpected, and is really uncomfortable. I really am hoping to shed some light on this.

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