1999 Isuzu Rodeo Question not accelerating

I recently got my oil changed where the air filter was replace shortly after leaving the place my check engine light came on and when at a red light trying to accelerate at a green light it felt as though my car was not moving. It didnt do this before. When I stepped on the peddle it would not go above 50. Then light went off a day later but accelerating was still hard and the engine was making a buzzing noise whenever I stepped on the gas peddle. The next day the light came on again. The light goes off and on but the car seems to be struggling to accelerate. What should I do