Left side back pain. Too serious?

I was told by a doctor that it's paraspinal muscle spasm caused by lifting something too heavy. However, I don't remember lifting anything heavy. This pain started suddenly. And there's a spot in between my upper and lower back that hurts when pressed too hard. It's more than a month now. Sometimes my lower left abdomen and my shoulder plates also hurt. And sometimes my left neck starting from the ears also hurts. But it happens sometimes not all the time. I can move around but get tired easily. A couple of days ago I had a headache that stopped after a head massage. I'm regularly using a gel and heating with a hot water bag apart from ongoing homeopathic medication. My previous medication wasn't homeopathic and it caused too much acidity. I feel a bit scared. Is there any possibility of something too serious?