Looking for advice – recurring lower back injury after lifting, improving but not fully recovered

About a month ago, while lifting an 8–10 kg sack at work, I felt a sudden pulling sensation with an electric shock-like pain in my lower back and right lower lat area. The pain was around 3/10. I rested for the next 3–4 days, and by day 5 I had almost no pain, so I assumed I had recovered and returned to the gym.
About a week later, while picking up a dumbbell from the floor for chest press, I felt the same pulling sensation again, but much milder. I continued my workout. The following day I went to the gym again because I had almost no pain. However, while lifting a dumbbell off the rack, I suddenly felt another pull followed by a very intense electric shock-like pain in my lower back that almost seemed to travel into my right leg.
I sat down for about 5 minutes, and the intense pain settled. After that, I was left with an aching pain, mainly in the lower right lat/lower back region, which felt more like a muscle strain. That incident scared me, so I saw a physiotherapist the same day.
The physiotherapist said it didn’t appear to be anything serious. He prescribed medication, gave me some exercises, and performed ultrasound therapy. I continued the exercises over the next few days, but the pain kept coming and going. My biggest problems were:
Morning stiffness and soreness in my lower back.
Pain around my lower right lat while riding rickshaws or electric tricycles.
I went back for follow-up sessions, where he added more exercises along with red-light therapy and ultrasound.
Because I was worried about a disc bulge or sciatica, I also consulted both an orthopaedic surgeon and a neurologist. They reviewed my X-rays and both felt it was mechanical low back pain, not something that urgently required surgery or other intervention. The neurologist advised me to continue physiotherapy and said that if the pain worsened or neurological symptoms developed, I should get an MRI.
I’m currently taking the neurologist’s medications and continuing my exercises. Right now my pain is essentially 0/10 while on the medication, but I don’t feel like I’m actually healed. I’m worried that once I stop the medication, the pain will return. At this point, physiotherapy doesn’t seem to be making much difference.
A few important points:
The pain is mainly in my lower right back, around the lower lat and near the right SI joint/hip area. When it occurs, it’s usually only 2–3/10 and doesn’t last long.
The pain occasionally shifts to the left side, but that’s rare (maybe once a week).
Every morning I wake up with lower back stiffness and soreness.
I occasionally get brief tingling in a few toes, but it lasts only a minute or two and isn’t constant.
Walking is generally pain-free. Sitting on bumpy rides seems to aggravate it much more than walking.
Has anyone experienced something similar and made a full recovery? Do you think this sounds like a lingering muscle injury, SI joint issue, or something that still warrants getting an MRI? I’d really appreciate any advice or experiences.