Being self-employed and residing overseas is not a bar to your entitlement to draw social security benefits because of age.
As a US citizen you were required to file US Federal income tax returns regardless of where you lived. If your income from self employment over the years was your only source of income you should have filed Schedule C and Schedule SE on your Federal Form 1040. These forms calculate the FICA (social security) and medicare tax - both of which you were required to pay as part of your annual income tax return process. In so doing you are making your contributions into the FICA/Medicare system and, provided the required period of participation was met (40 qualifying quarters) you should qualify for the benefits of social security.
Note that FICA and medicare are not "deducted" when a person is self-employed. That happens when one is an employee and receives a Form W-2 at year's end. As a self-employed person there is no employer to "deduct" (that is "withhold") FICA/medicare (1/2 applying to the employee and 1/2 applying to the employer).
If you were married to a person who may have qualified for the US social security benefits and that person had higher income than you and (perhaps) is now deceased it might be possible for you to draw from the benefits of that person. If you were, on the other hand, married to a non-US citizen then this possibility would not apply in your case.
At any rate, you should consult the servicing office for social security at a location near to yourself. There is a wealth of information on the US social security website - but it is always better to talk face-to-face to a person because the rules are very confusing and difficult for average people.