How many days after taking Lomexin vaginal suppository should I abstain from sexual intercourse?

Not too long. When you insert a suppository give it at least an hour or more before having sex (you can get this in cream form as well and is much more convenient.) By waiting an hour or more it will give the suppository a chance to melt (quite rapidly) from your body heat.
3 days. This is an antifungal vaginal suppositry and should cure your infection within 2-3 days.