Ok - first and for most you have to take note that most of the advice you are receiving on the sex part will probably have to wait until after the baby is born.... for this is a trying time for your wife, both physically & emotionally (and) Yes, sex is the last on her mind right now.... PATIENTS is the key word for you and the next couple of months.

IMO - men need to realize that a woman needs to be loved and pampered out side of the bedroom and on a daily or weekly basis for her to respond in the bedroom - she needs to feel special, loved and seen as beautiful to you before she can give of her self.... are YOU aware of this fact? - if not make it your main goal from this day forward.
Keep in mind that she is more like a crock pot (needs to simmer to boil) and that you are probably more like a microwave.... a one touch button and you are ready to pop / heat.

IMO - the age difference here could be a factor in all of this as well.... you are 25 and still in your prime of life wanting and thinking about sex often.... were as your wife is starting to see life in a different view, were sex is nice but other things rank higher on her personal list - like having a family before her biological clock runs down.

Maybe try dating your mate again and making her feel special above all other females in this world and in your eyes..... like you did when you first meet - let the WOW return.

IMO - when a relationship has a problem in any area of life - it is telling both parties that something needs to be fixed... and it always takes two to create an issue, never just one, so look at what you may have done to cause her to retreat from you sexually and start from there.... improve you first and then she will follow..... with time, love and patients.

I personally cannot be sexual with my husband if I am feeling rejected, unwanted or wounded by something he did or said... past or present - mends must be made.

LoVe,
Rhapsody - ((( hugs )))