Why do my contact lens start irritating my eyes after a few months of usage?

Over the last year and half, i have bought over 10 pairs of contacts and each of them starts to irritate my eyes in 1 or 2 months. I have tried different companies including Bausch & Laumb and Comfort. (Supposedly the best ones available in Pakistan) Each time its the exact same problem, and either my left or right eye has a scratchy feeling a few hours after putting in the lens. When i remove the contact the irritation goes after but it feels like i have a grain in my eye which takes about 15 mins to go. Any answers are highly appreciated. Should i change my lens brand or have my eyes checked. Please tell.

Read more: Why do my contact lens start irritating my eyes after a few months of usage?