lately, everytime we turn on the shower, the toilet bubles. when we try to flush the toilet, it doesn't flush, it just drains slowly. if we don't use the shower - like overnight, the first flush in the morning- the toilet will flush normally for the one time - then it again doesn't flush - it just drains slowly. at time we'll hear air buble in our tub if the toilet flushes. we have a stand up shower and a separate tub - jacuzi in our bathroom. the shower seems to drain ok. it's just when the toilet drains slowly, the tub also drains slowly...

help!

thank you