More than likely your boyfriend can claim you as a dependent on his income tax returns and would file as head of household. The rules are a bit intricate when it comes to individuals such as yourself, so you and your boyfriend should first read through the instructions to Form 1040 regarding dependents to see if you qualify as his dependent. The IRS also has an online interactive form you can use to try and figure out if your boyfriend can claim you as a dependent. The interactive form is on the IRS' website here: http://www.irs.gov/uac/Who-Can-I-Claim-as-a-Dependent%3F
If you and your boyfriend still cannot get a good answer, then I would strongly advise the two of you to consult with a competent local tax professional, such as an accountant or a CPA.
Lastly, you say that you receive child support; does your child also live with you and your boyfriend? If so, have you considered whether or not your boyfriend could claim your child as well, or is the child's father already claiming the child as a dependent?
My answer does not constitute legal advice and may not be relied upon by anyone for any purpose and does not constitute an attorney/client relationship or an offer to form such a relationship. This disclaimer is intended to be fully compliant with the requirements of Treasury Department Circular 230 and the terms thereof are fully incorporated by reference. If you wish to consult with me please contact me at dana@nytaxcounsel or visit my website at www.nytaxcounsel.com