let your midwife know when you see her next but it is not an emergency situation. women lose it at different times during pregnancy it can actually regenerate. at 34 wks it could be a sign that labour could happen in a few weeks but not necessarily any moment now. regular contractions are the best indicator of labour or your waters breaking. nothing at all to be worried about, the mucus plug, Braxton hicks the lightening or engagement of the baby and even starting to dilate or effacing can mean your time is near but you may also very well be pregnant another 6 wks or more. if you notice any more obvious signs of labour then yes call your midwife, but i think just mentioning it next appointment would be enough and maybe see can do an internal exam to see if there are any other changes to your cervix, but even that isnt too reliable. luke mentioned already if you are dilated like one or two cm you can sit there for weeks. good luck mama hope thats helps!
If you was 22 weeks I would be worried.. you are near the ending of pregnancy everyone pregnancy is different no two pregnancies are alike.. just because you lost it now it could be weeks before you give birth.. I'm 37 weeks I have yet to lose mine and my baby breech.. so don't worry just talk with your doc