Take off your wipers and give them a proper wash and wipe any road grime off. if your cleaning your windscreen and not your dirty wipers, that might be the issue. have you got glass cleaner? AutoGlym Fast Glass is good. Failing that, get hold of some IPA cleaner and wipe over the windscreen after a wash. Maplins sell it diluted. If youve not had the car long, the previous owner may have used too much polish/product. Rain-X is pretty good but needs regular top up treatments
Hope that helps