I took a learning disability test at age 55. At that point, I was told I must have had an early brain injury (which would explain a lot)(I was trying to finish my senior year at university). Is it possible I would qualify for SSI? And would that 'mess up' my Social Security at age 70?
Yes, depending on your age, earnings history, income and resources, it's possible that you might qualify for Social Security disability benefits (SSDI) and/or Supplemental Security Income (SSI). However, your condition would have to be considered disabling by Social Security's definition. The basic requirement is that your condition be severe enough to keep you from being able to do any substantial gainful work, and be expected to last for at least a year or result in death.
The only way to really know for sure if you would qualify for benefits would be to file a claim with Social Security. If you do qualify SSDI, that would not 'mess up' your age 70 Social Security since you could still suspend your benefits at full retirement age (FRA) in order to accrue delayed retirement credits (DRC) until age 70. However, if you receive SSI, which is a needs based benefit administered by Social Security, then you would be required to file for your Social Security benefits as soon as you're first eligible. By the way, if you meet the income and resource limits for SSI you might be able to qualify as soon as age 65 even if you aren't considered disabled.
You may want to consider using our maximization software to explore and compare your various options so that you can determine your likely best strategy.