I totally feel for you. I’m a native Welsh speaker who is learning French and Russian. Your difficulties are very common. Mostly likely, you are learning Welsh from material written by native English speakers. I’ve checked quite a few learn Welsh language materials and it’s surprisingly difficult to find material written by people’s whose actual native language is Welsh! Most Welsh learners are unaware of the issues that can come along with this. I’m not saying they’re really bad, I’m just saying that sometimes I find the things they teach or say quite odd, or just don’t sound right to native speakers. They then pass on those things to you where they might cause confusion.
Also, a lot of formal material is still, well, too formal! It just doesn’t match spoken Welsh! Drives me crazy! I know so many learners that are so put off learning Welsh because of this!
I’m not sure if you will find it fun, because my blog is to do with my interests or experiences, but I’ve tried to plug this gap that learner have. It’s probably too advanced for you, but you will certainly find the explanations of contractions very, very useful!