Not sure if you noticed, Hennerton, that it is 'Total T3' which has been measured, which is always much lower than free T3.
The free T3 is really the one which will give you some clues, emmaw79. The fact that you are suffering symptoms suggests that somehow the medication is either not working or you need a higher dose, but without the range for the free T4, and the free T3 result it would be difficult to pinpoint the actual reason. 175 could actually be too much even though you are still hypothyroid, particularly if you are not converting.
There are many reasons why this could be the case, the first thing to look at is your vitamin and mineral levels, notably ferritin, Folate, Vit B12 and Vit D. If any of these are less than optimal, it could hinder conversion. Another thing which could hinder conversion is low adrenal reserve, because the cortisol produced by the adrenals is also needed to convert.
The primary thing to look at is the free T3, that definitely has to be the starting point. If that is low, conversion is a problem and you need to find out why. If it is high, then reverse T3 would have to be considered.
It all sounds very complicated, but it is actually simple. The first step - measure the free T3.