It sounds as if you have spun wool thread for sewing, which is not, historically, often used for strong seams but will match your fabric.
Beeswax really helps smooth fuzzy fibres.
Using a short length when sewing, 12" rather than yards also helps the sewing to be strong as each length doesn't have to go through the fabric multiple times.
If you iron the creation after sewing the beeswax melts into the surrounding fabric (usually invisibly) and this also strengthens the seam.
I spin linen thread (wet spun, long fibre) for sewing as well as in the garden, I'm not good enough yet for very fine work but the long fibres make even a single very strong and good enough for linen bags etc.
In the 18th century wool cloaks etc were often sewn with silk thread where the seams need strength.
Hope that helps,
