I know the other people who answered said that you should say "if it wasn't so difficult", instead of "weren't", but actually in British English, weren't is correct and is used in written English. Lots of people say "wasn't" in speech though. Your sentence is perfect

That is totally fine. You have the third conditional in there used perfectly. Please ignore when people say you can't use weren't. In American English you can use wasn't but in British we absolutely can use weren't in this situation.

Your sentence is perfect. I agree with Aisling and Paul that 'weren't' is 100% correct and that you should ignore the people who tell you to say 'wasn't'. 'If it weren't' is a subjunctive to indicate a hypothetical situation. Just one thing to add: Previous answers have given the impression that this is a GB/US difference. It isn't. It's a difference between casual informal English where 'wasn't' (the indicative form) is acceptable, and more formal/traditional English where the subjunctive is required. This distinction is common to both GB and US English, and, in fact, educated US English speakers are MORE likely to use correct subjunctives than their British counterparts.

Just the last one, better to use wasn't so difficult.

Thanks Charles and Bernabe!