Ah.
There's the problem.
It's too little Ram / not enough to allocate to MC to play with 50 mods
Assuming your computer takes ~2Gigs with NOTHING open, just to run windows,
That would cut it close.
MC allocates 3Gigs by default as i remember and depending on your mods that you have installed,
If most of them add more blocks and etc., try allocating more ram to minecraft.
My friend has 6Gigs of ram also and a crappy PC, he can run MC at only ~20 FPS. No mods.
Whenever i play Skyfactory3, it has 180mods, I have to allocate 6Gigs to MC to play smoothly.
It also takes ~20 minutes to load.
I have:
Intel Core i5-4590 @ 3.30GHz
16 Gigs of DDR3 RAM
Correct me if I'm wrong guys please and ill edit the post. I don't want to give out false info.