As you had described i would suggest to go to physician as soon as possible.
Normally i recommend to take rest for some days but as your problem i read, i would only recommend only to concern physician.
And another suggestion is please try to away for some days from intercourse because it will hurt you more than enjoyment.
So, Talk with your partner to not having intercourse for some days, till concern physician and what he/she suggest follow strictly.
If you still want remedies than keep resting and use Heat/Ice Packs.
It help relieve most types of low back pain
by reducing inflammation.
Often patients use ice, but some prefer heat. Both may be used alternately.
Hope you will find it out helpful.
Thanks And Regards,
Dr. Gaurav Prajapati