I travel a lot between timezones. Basically if it is a one time thing with more than 4hours difference like yours, I push myself to not sleep the first day. This means I go without sleep for 30-50 hours depending on the timing and then go to sleep at a normal local time (23-24 at night). My theory is that after not sleeping for nearly 2days (1day is travel time usually) the body is sleep deprived a lot and forces the body clock to shift very quickly in order to get some needed sleep. Before I just took it a small step each day to adapt and it took me around a week and I was pretty tired the whole time. Using my method, I have to find something to do the first day after flight to make myself from going to bed and it requires some self-control, but after my 1st proper sleep I am pretty much ok. Its important that you dont oversleep, 10hours max (I go straight to my 7,5) or it wont have the effect. This way you are ok after 2days instead of 7-10.
I am sorry this will not be of much help to you, more like a something to try next time. I am afraid there is not much you can do in your situation just wait it out. However if you feel up to it try not to go to bed for 20hours or so and go like you normally would at night local time (you should be really really tired for this to work). This should force you to sleep and you should be better next day. I use this to correct my sleeping pattern when its messed up such as after night heavy drinking, partying, sex etc. The key in both is to make yourself sleep-deprived then force your body to sleep against your natural clock thus forcing it to shift.
It is counter-intuitive that less sleep in total makes you better. However its not the length of sleep that matters, its the quality. Human body can work properly with as little as 2 hours of sleep per day. I did that for 2 months myself with no negative impacts, look up uberman polyphasic sleeping if you are interested.
Good luck, hope this helps, at least for next time. And NO sleeping pills or coffee etc. it just makes it worse.
Good luck