Grounds for annulment vary slightly from state to state. Generally, they may be obtained for one of the following reasons:
Misrepresentation or fraud -- for example, a spouse lied about the capacity to have children, stated that she had reached the age of consent, or failed to say that she was still married to someone else.
Concealment -- for example, concealing an addiction to alcohol or drugs, conviction of a felony, children from a prior relationship, a sexually transmitted disease, or impotency.
Refusal or inability to consummate the marriage -- that is, refusal or inability of a spouse to have sexual intercourse with the other spouse.
Misunderstanding -- for example, one person wanted children and the other did not.
These are the grounds for civil annulments. Within the Roman Catholic Church, a couple may obtain a religious annulment after obtaining a civil divorce, so that one or both people may remarry, within the Church or anywhere else, and have the second union recognized by the Church.
Most annulments take place after a marriage of a very short duration -- a few weeks or months -- so there are usually no assets or debts to divide, or children for whom custody, visitation, and child support are a concern. When a long-term marriage is annulled, however, most states have provisions for dividing property and debts, as well as determining custody, visitation, child support, and alimony. Children of an annulled marriage are not considered illegitimate.
There are no annulment forms.
You have to file the pleadings in a Complaint which must be accompanied by a Summons. These must be filed and served on your spouse. If you cohabited with your spouse for even one day, then you must have grounds for fraud and deceit.
Would you try to do surgery on your own hand?
For a small matter like a splinter, sure, you might. But if you don't know what you're doing, you'd pay a surgeon. What if you thought you had a jammed finger and tried to yank it out, but it turned out to be broken? Self-diagnosis and treatment may have been cheaper, but in the end would make it worse. In the same way: Unless you are certain about what you are doing or have no other option, it's usually better to hire a lawyer. In case you can't afford a lawyer, I will attach a link (below) for self-represented litigants in divorce cases.