Mak,
You may not have done anything wrong, when in doubt ask who you are following (type acft, and if necessary color). If you are still in doubt ask ATC to call your turn to cross wind, down wind, or base and to point out who you are following again.
I'm a controller in the US, so when I have multiple acft in the pattern and someone else joins the fray, I will say that you are number X following the yellow and white C172 and its' position in the pattern, or what ever the acft is, advise when you see your traffic (I've worked pattern traffic with as many as 12 acft in the pattern). If a don't get a I got my traffic I'm following, soon enough I may either point it out again or I'll say I'll call your turns, depending on what I feel is necessary to keep the operation safe.
Mike