Being separated for nearly 5 years doesn't count as being divorced - even being separated for 50 years wouldn't amount as divorce - but it does mean that you're approaching an important legal milestone in relation to divorce proceedings.
If a husband and wife live apart for two years, a divorce can be obtained on the grounds of separation but both partners must agree to this. (It's also possible for one partner to seek a divorce, without consent from the other partner, on the grounds of 'desertion' but this can be much harder to prove than simple 'separation'). However, after a married couple have lived apart for 5 years, one partner can divorce the other without the need for the agreement of the second partner. So, unless you know that you can contact your husband easily, and that he'll agree to the divorce, it might be best to wait until you've been apart for a full 5 year period; this will make the divorce process much simpler.
http://www.direct.gov.uk/Parents/FamilyIssuesA ndTheLaw/Divorce/DivorceArticles/fs/en?CONTENT _ID=4002976&chk=2NiWQa
Chris