Can hair thickness increase?

[ChloeDharma]

Thickness can fluctuate for lots of reasons other than the obvious layers cut in or grown out.
Hair is often a reflection of general health, diet, excercise, illness, stress, scalp health, handling etc all can effect it.
Surgery can cause the body to suffer extreeme stress and often after an extreeme stress on the body a condition caused telogen effluvium can be caused. This is the body reacting to stress by making a large number of hairs prematurely exit the active anagen phase of the growth cycle. They then shed anytime up to 3 months later and can take up to a year to grow back.
Illnesses like diabetes, lupus, thyroid problems can all cause excessive shedding as well.

Given your hair has thickened dramatically it would seem something has changed. Some people find that chemicals like sulphates, or waxy/coney conditioner on the scalp increase shedding, if you have cut these things out or changed the types of chemicals used then it would indicate not that your genetic potential for thickness has increased, but that before something was preventing you from reaching your genetic potential.
I notice you use SMT's and oils, if you oil the scalp then something added to the oil, or the type of oil itself may be having a beneficial effect in reducing shedding or stimulating growth....aloe vera is also considered good for hairloss and for stimulating growth so it could even be that.
Anyway, whatever it is, congratulaions and just keep on doing what you are and enjoy the results