I am a California attorney and cannot give legal advice in your state. My comments are information only, based on federal law and general legal principles. YOUR STATE MAY HAVE ITS OWN LAWS THAT OFFER SIMILAR OR GREATER PROTECTION. If I mention your state’s laws, it only means I did a quick Internet search and found something that looked relevant. You MUST check with an attorney licensed in your state to learn your rights.
Without knowing the company, the industry, your job, the decision-makers at your company, the employer's policies, your work history with the company, and a lot more, no one can even begin to answer your questions.
If you want a reduced schedule due to a disability as defined by the Americans with Disabilities Act of 1990, 42 U.S.C. sections 12101 et seq. (ADA), you may be able to get it as a reasonable accommodation. To do so, however, you would need to disclose your medical condition. Please look at my Avvo guide on the ADA: http://www.avvo.com/pages/show?category_id=6&permalink=disability-discrimination-in-employment.
The Family and Medical Leave Act, 29 U.S.C. section 2101 et seq. (FMLA) can also require an employer to provide a reduced work schedule if the employer is subject to that law and the employee qualifies. Please look at my Avvo guide on the Family and Medical Leave Act, 29 U.S.C. section 2101 et seq. (FMLA): http://www.avvo.com/pages/show?category_id=6&permalink=family-and-medical-leave-fmla-summary-of-key-provisions.
Other than those laws and company policies, the employer does not have to allow you to work an alternative schedule. If your personal reason is compelling and sympathetic and you disclose it to the employer, you may have a better chance of getting what you want. If you do not want to disclose the reason under any circumstance or the reason is not one the employer is sympathetic to, you may choose not to disclose it. But as you noted, the employer can just say no.
One consideration if you do not disclose is the employer may think the reason is other than or worse than it is. The employer may think you are not a team player, have another job, are going to school and will leave as soon as you get a better job, are in a drug rehab program, or something else. The employer may decide to end your employment rather than wait for any consequences to develop.
There is no law that requires an employer in the private sector to provide benefits to employees other than the limited extent required by the new federal health care law. Generally, an employer can decide whether to offer benefits, what benefits to offer, and to whom the employer offers them. There are restrictions that prevent an employer from limiting benefits to employees BECAUSE OF their race, religion, disability, sex, age (40 and over), national origin, pregnancy, genetic history, and in some states, because of their sexual orientation or marital status.
Also, an employer is free to define "full-time" and "part-time" as it wishes. There are no laws in the private sector that designate any particular number of hours as full-time or part-time.
Given this, the employer can define employees as part-time even if they work the same number of hours as full-time, and limit benefits to those employee the employer has defined as full-time.
If, however, there is a company policy that defines all employees who work a certain number of hours as full-time, you may be eligible for that classification. But language can be tricky. For example, a policy that says "All full-time employees work 40 hours per week" is not the same as "All employees who work 40 hours per week are full-time."
Also, if your job is covered by a contract between a union and the employer, or if you have an individual contract, the employer must comply with the terms of that contract.
It isn't fair and it isn't good social policy. But it is legal.
I hope your situation resolves. I wish you the best.
*** All legal actions have time limits, called statutes of limitation. If you miss the deadline for filing your claim, you will lose the opportunity to pursue your case. Please consult with an experienced employment attorney as soon as possible to better preserve your rights. *** Marilynn Mika Spencer provides information on Avvo as a service to the public, primarily when general information may be of assistance. Avvo is not an appropriate forum for an in-depth response or a detailed analysis. These comments are for information only and should not be considered legal advice. Legal advice must pertain to specific, detailed facts. No attorney-client relationship is created based on this information exchange. *** Marilynn Mika Spencer is licensed to practice law before all state and federal courts in California, and can appear before administrative agencies throughout the country. She is eligible to represent clients in other states on a pro hac vice basis. ***