Are my past good deeds erased?

I have been a good Muslim and a bad Muslim. Throughout the years I've been to *'omra* (a few times) and *hajj* (once) and read the whole Quran (once) but also been neglecting prayer and doing sin (drinking, gossip, etc...). My faith keeps going up and down, sometimes even going months without prayer (because of bad influence around me). My friend tells me all my past good deeds have been wiped away because of my bad sins and neglecting prayer. Also that all the performing of faith in Ramadan and *hajj*/*'omra* was a waste of time because none of the good deeds from that is counted and is replaced by bad deeds. My friend did not provide any evidences to support this claim, so I'll ask here: **Is there an Islamic basis to this idea that all my past good deeds are wiped away due to my sins?** Is this actually an Islamic teaching, or is it based on an incorrect understanding of Islamic fundamentals?