I have chronic sinus problems and every month it seems to flare up and when I get an attack the pain is excruciating 
I get no warning of when it's going to happen, it just starts with a frontal headache and goes from there. No matter what I do I can't stop it from developing. The pain is so bad I feel as though someone is hacking my skull open with an axe. I have a reasonable pain threshold, but this is just agony.
I do a sinus rinse, take some mucous thinner, paracetamol, ibuprofen, steam, massage and bed. I knock myself out with Night Nurse and try to get some sleep. By the morning, it's usually at a level that I can manage, so I keep doing the sinus rinses and just take paracetamol.
What's the strongest painkiller I can buy to deal with this as I can't cope with the severe pain. I have taken MIL's tramadol in the past because I've been so desperate.