99 Cougar No Acceleration and Shaking

[xxterrencexx]

ok so im not sure whats wrong here but i think its a plugged exhaust or clogged catalytic converter but whats happening is when I drive my car is lacking power huge, sometimes ill push on the gas and it will hardly move and start chugging but if i push down more it will go. When i go on on ramps to the highway as soon as i hit 70km it starts to chug then i have to push the pedal to the floor to get going,then after a while the car will start to shake after 5-10 minutes of driving and i have to let it cool down or it will keep shaking or just go back onto city roads and it doesnt shake as bad. Once im off the highway my car will begin to shake more at 20km and 60km i have no clue why, any help would be huge thanks