clogged/ slow drains

OYE VEY! I need some help! I had a new tub and shower liner put in around the middle January. Since then my tub drains super slow and the kitchen faucet has next to no water pressure. I have tried draino and it helps a litlle but it's short lived. Any suggestions for either one would be greatly appreciated!!

Do you think something may have occurred with the pressure (Like a vacuum effect?) due to the liner? Have you tried to have someone "snake" the drains? I know that if you have trees or shrubs near the home - especially big trees, the roots are so deep that they can interfere with the plumbing and cause a back up.

We have the issue of: if the dishwasher is on, as well as the washing machine and if I drain the kitchen sink after soaking something... things will back up downstairs and it reeks! LOL. So I learned not to do that after the third time! :)

Best of luck! ;)