Infestors

I use creator primes, mass immortal stalker sentry play in pvz, but I always lose to infestors. No matter what I do, he just holds my army in place and shreds it with ling roach, even with good force fields, he just slowly whittles me down while expanding, getting hive tech, and slowly pushing into my bases. I can't figure out how to deal with this, the best solution I can think of is to get collos for the splash on the lings and the range, but they take a lot longer to get up safely so I lose my ability to be aggressive mid game :( pls help