frister rossman nothing happens when i push pedal!?

When I push the pedal on my machine it 'revs' but the needle does nothing, unless i jult the machine or wiggle the wheel, then I can sew until i have to stop and then I have to repeat this awkward process just to sew for a very short time. what is wrong and how do I fix it? (drive belt??) i would like to fix this myself as no repairs near me and expense. Thanks.