HTLV-1 usually is acquired from a IV drug user or blood contact. It is very very rarely obtained from sexual intercourse and that is usually not in the U.S. Although it can happen it is rare. Most cases are Lymphoma or leukemia and those are inflammatory are usually IV drug use and only rarely by sexual contact and not usually in the U.S. As for the window period I only saw one article and the window was very long such as 2 years.
HTLV 2 is usually also acquired by sharing needles or by breast feeding.
Here is something from med help.
http://www.medhelp.org/posts/STDs---STIs/HTLV-Window-Period/show/1748643
This is from a previous question.
I assume you have been tested for Syphilis and Gonorrhea (GC). GC can sometimes get into the joints if left untreated and syphilis test has a 20% false negative rate so if you had the RPR you may want to get re-tested using the FTA-antibody test if you are not from outside the U.S.
Regards,
mkh9