Welcome to Just Answer.
Sorry to hear about your problem.
It has to be a venting problem; air bubbles are a sure sign that the main vent pipe is partially clogged from an animal getting caught or a bird building a nest, snow/ ice, etc. This would effect proper draining as well. The vent sucks in air and replaces the displaced water, allowing it to drain properly; it can be compared to holding your thumb on the end of a drinking straw that is full of water; the water will stay in the straw, until you lift your thumb, allowing the air in. A high pressure nozzle, on the end of a water hose, can be used up on the roof to spray down the main vent pipe. This is effective at clearing blockages in the vent pipe only; often the vent pipe can be augered as well. See short video below for more information.
If you need further help or clarification on this answer, please do not hesitate to reply to this post.
Thanks for asking your question at Just Answer.
Best of Luck, Brian