Need advice on Dublin trip.

Would you be interested in renting a car for a morning while you are there? Lovely places like Glendalough (in Wicklow) or Newgrange (in Meath) are fairly close, and you'd get to see some of the Irish countryside as well as Dublin (which is a great city, but a city nonetheless).

I haven't lived in Dublin in six years, but Kennedy's pub (near Butt Bridge) had the most amazing Guinness I've ever tasted in my life. It's the only place I'd consider getting a pint of Guinness rather than a glass.

And book dinner somewhere for Valentines night...

I would disagree with number 2 who said three days is too much for Dublin. There is plenty to see and do in that time period.

February is perfect for a Dublin visit. No crowds or queuing. You've been given plenty of Pub advice - I'll add Hartigan's Pub on Leeson Street an amazing pint and atmosphere you could bottle and bring home with you! Three days is too short - by the time you arrive on a long haul flight (jet lag etc...) get aquainted with your accommodation and surroundings and transport options. A great way to see Dublin's must see attractions (especially allowing for pregnancy etc..) is the official Dublin Bus Hop On Hop Off City Tour. The tour with commentary takes one and a half hours but your ticket is good for twenty four hours. Ticket also allows you a discount on the entrance fees.
Dublin is lovely at any time of year.
Welcome to our lovely city.