There is really not enough information here, but let me answer this in 2 parts.
First, to get SSD benefits, you have to show you are unable to do any substantial gainful activity. This means showing you cannot do you your old job OR any other type of work anywhere in the US, after they consider your age and education, medical problems, and work history for the past 15 years. if your medical problems only get you a 4 to 6% rating, I am doubtful that is not enough.. But, you may have other medical conditions - physical or emotional (depression? high blood pressure? seeing problems? etc) that could be considered with this impairment to show you meet SSA guidelines.
Second, if you are getting early retirement, your benefits are reduced by about 25-30%. if you get SSD, then Social Security would bring your benefit rate up - probably not to the full 100%, but it could get close.
Finally, you say you are getting workers comp. If you do get awarded SSD benefits, they will likely reduce the SSDI benefits you receive (in some states they reduce the workers' comp) as there are limits on how much you can get from Social Security and workers' compensation at the same time.
You may want to talk to an attorney in your area so you can review the specific facts with counsel. If you do not have an attorney, there are a number of good attorneys in your area, some of whom you can find here on Avvo. Use the “Attorney Finder” feature of Avvo for help with that.
Most attorneys who do any amount of Social Security work are members of the National Organization of Social Security Claimants' Representatives (NOSSCR) and provide a free initial consultation. In any event, no attorney may charge a fee for work on a social security claim until it has been approved by Social Security. The fee limit is a maximum of 25% of past due or back due benefits you are owed, and many lawyers charge less than the full 25%, and the money is not paid until your claim has been approved.
You may contact your local city, county or state bar association to see if they have a lawyer referral program, or you may contact your local legal aid office if you cannot afford an attorney.
You may also contact the NOSSCR for the name and email address or telephone number of attorneys in your area. The telephone number for the lawyer referral service of NOSSCR is 1-800-431-2804. NOSSCR's website is www.nosscr.org.
In addition, you can find a Board certified specialist in Social Security by contacting the National Board of Trial Advocacy. They evaluate lawyers (independently) in many types of claims and require extensive experience and testing before a lawyer is certified. They have a section specifically for Social Security: The National Board of Social Security Disability Advocacy, Divisions of the National Board of Legal Specialty Certification.
Their link is: http://www.nblsc.us/
The exact answers to questions like this require more information than presented. The answer(s) provided should be considered general information. The information provided by this is general advice, and is not legal advice. Viewing this information is not intended to create, and does not constitute, an attorney-client relationship. It is intended to educate the reader and a more definite answer should be based on a consultation with a lawyer. You should not take any action that might affect your claim without first seeking the professional opinion of an attorney. You should consult an attorney who can can ask all the appropriate questions and give legal advice based on the exact facts of your situation. The general information provided here does not create an attorney-client relationship.
I agree with Mr Farrells answer and would add that it may only increase the amount that you get slightly. In Colorado the WC would be taking an offset for the SS, however if you have an atty for the workers compensation case they should be able to help with both the social security and to answer that question for your state