Usage of "boli" / bolą

my lodger and i both got back from work at the same time yesterday. he wanted me to go to the shop. i said to him nie moge bo moje stopy bolon(hope i have spelled this correctly, as have learned only by conversation).later on i asked him why for example it is bolon and not boli, as in moja glowa boli.i have come to the conclusion that if you have 2 of something eg arms, legs, you use bolon and not boli.my lodger started testing me to see if i understood. he asked if my back hurt, so i said moje plecy nie boli.he said moje plecy nie bolon.presume he is right as he is far from stupid.now i am confused. help! this is probably about as clear as mud....

plecy is plural without singular in Polish that's why they bolą (there are a couple of nouns in Polish that only have plural form: drzwi (door), sanie(sleigh), nożyczki(scissors), spodnie(trousers), majtki(pants) etc- the concept is not alien to English language either - you have scissors and trousers too)

btw -ą ending is regular and pretty consistent throughout all verbs ( robię - I do, oni robią - they do; one skaczą - they jump; artyści malują obrazy - Artists paint pictures.)

thanks gumishu, guess i wont be a polish professor anytime soon.! cant believe i mistook ą for on! think i am going backwards instead of forwards!!

nah, it's just the way Polish people pronounce their own language typically - we often say bolom instead of bolą (or at least something half way from both forms - and this inbetween sound can well be perceived as bolon)