How soon after getting married can you file for divorce?

The state of Illinois makes getting a divorce more difficult than others.  You can file for either a fault or no-fault divorce.

To file for a no-fault divorce you must separate from your spouse for six months or two years (as applicable). When you file on grounds of no fault, this basically means it was no one's fault that the marriage didn't work out; you and your spouse had "irreconcilable differences."  If both of your agree to end your marriage, you must maintain separate residences for 6 months, both sign a form that you are in agreement, and submit it to the court.  If only one spouse wants to a mandatory 2-year separation period that is applied.  After 2 years of separation, a divorce can be granted for any reason.

To file for divorce based on grounds of fault, there is no mandatory separation period required; your suit can be processed through the court system more expediently. In fact, your divorce can be final in as little as 90 days.  However, if you file on grounds of fault, you are charging your spouse with breach of the marital contract by accusing them of one of a number of grounds.  they grounds of adultery, impotence, abandonment, habitual drunkenness or drug addiction, extreme cruelty, felony conviction, transmission of a sexually-transmitted disease to you, or bigamy.

Since I don't have more of the details of your case it's hard to say.  Also, you may even be able to get an annulment but that also take time and again, without knowing the specifics of your situation, its hard to say whether or not one would be available to you.  Right now you should consult with a divorce attorney in your area.