My digital ovulation stick just came up smiling face this morning...im day 18. and my cycle is usually 28 days. is it possible to naturally conceive?

Yes, possible: Yes still possible to conceive. Not every menstrual cycle is going to be the exact same length. The follicular phase (1st half) of your menstrual cycle is variable and is determined by how long it took you to grow a mature follicle. If you still have a 28 day cycle this month then you might have a luteal phase defect and you would benefit from ovulation induction meds (i.e. Clomid).