I believe you can take it a maximum of three times a year, if that applies to you. Also, I think, for AAMC, you must send then a convincing letter after the third try saying you still want a shot.
One said yes and the other said no lol. And im planning on taking it twice this year IF i have to and if worse comes to worse than id take it again in jan.
I've seen threads of ppl accepted into MD/DO having taken MCATs over 5 times....the only rule or point I've seen enforced is the three tests per year. Otherwise ur main goal should be to show positive trend.
My MCAT philosophy is to go into the test with a "one and done" attitude. Don't consider a second until after you receive scores for your first. Study hard for the first one and nail it.
What have your practice tests been. Do not kick more money to the AAMC until you adress the reasons why you are getting poor scores that you need to take the test again. Look on the MCAT forum on this for more help or feel free to PM me, might be able to give you more detailed thoughts.