Car has less power & makes a slight clanking noise.

[Basick]

Hello, i have a 1985-87 Cutlass Ciera. It has 150,000 Miles on it and has been running pretty good, until 2 days ago. It started off whenever i started the car, the engine seemed like it would rev itself up whenever the engine sounded like it was going quieter and quieter... almost like it was gonna die. Than after that whenever i drove the car, i noticed i had the press the gas more than usual to get to certain speeds.. like before i would press it slightly and i could reach 65mph on the freeway, now i have to press it down maybe an inch or two more than usual. Also when im on neutral, 1st, and 2cnd i can hear this kind of clanking noise in my engine, like something is hitting each other inside. It's not a fast one like a machine gun but kind of slow and goes faster as i excel. Please help me find out what is wrong or what it could be, also what could help. Thanks!