The reasons that you would have been given this injection are 2 fold,
1) to locate the root cause of your pains, including, what level they are.
2) to offer you some temporary pain relief, which is 'hoped' might become
permenant
If they had injected the 'correct root location' of your transferred pains (such as sciatica) the relief would have been 'immediate' and you would have felt almost 'complete relief' for the first injection over a 4 - 10 week period. The second and subsequent injections would become less and less effective. Too many injections would seriously damage your soft tissue including muscles, cartlidge and discs.
I am very sorry to say this, but they appear to have not located your 'root location' and they appear be looking in the wrong place. I base this opinion on my own experince where I was misdiagnosed and mistreated for
over 3 years, Before getting a 3rd & 4th nerve root block in the correct level and the pain completely disappeared for 6 weeks.
You need to challenge you Doctors belief on where he/she thinks your root cause is, this won't be pleasent or easy and the Doctor won't like,
but if you don't you may suffer an unneccesary and prolonged period of pain just like me (3 years).
Best wishes
SPINELF