I had (well still have… passenger helmet?) a helmet that gave me a really bad pressure spot in the center of my fore head after about an hours ride – I took a lot of time to make sure that it fit properly before I bought it, and it felt great wearing it around the store, or even for a short ride. Many a rider told me to wear it for a while to break it in, or compress the form with my melon – I think someone even suggested that I rub it down with a baseball or a spoon – it just didn’t happen – the compressing of the foam! I rode occasionally with it as a passenger for several years and found that the sore spot lasted a couple of days after the ride – short hair, long hair, it didn’t matter. So, I bought a bike las week and after my first longish ride of 400km or so decided that I just couldn’t deal with it any more. I caved and bought a new one (and I didn’t spend a ton of money) which is SO MUCH BETTER! I think the old one just wasn’t the lid for me, and if I’d known how much better the new one feels I wouldn’t have waited all this time.
Good luck!