Mustard,
Allow me to offer a little advice. It may or may not be helpful, but it is my 2 CC's. First of all, no ultimatum when you have this discussion...this will not help and it probably isn't what you really want. Second, this is going to require alot of talking, patience and some skillful planning on your part. So be prepared to work or you will not have success.
There are a couple of tactics you could try (in addition to talking)... she needs to know you feel unsatisfied and under appreciated, you need to tell her this. You need to encourage her to talk about what the hold up is on her side. Then try to plan a "date night". @ least once a week plan an evening where you can go out and talk, dance, eat, laugh, have a drink, take a short trip, try to focus on this " Date Night" as an opportunity to talk and be closer to her. Find out more about what she is thinking. Also some women do not engage sexually just from talking. Some women need to have "touch" before their sexual feelings come into play...for example:
You could talk for hours about not getting any sex ...and still not get any. Or you can say "come here, and start to gently rub her shoulders, touch her ears, gently rub her neck and arms (whrever gets her started)...and with your soft touches you may be able to kindle a fire and get her excited...also you need to have sex in a manner that gives her pleasure, dont just cum and roll over and go to sleep.
You may tell her how attractive she is to you while you are rubbing her shoulders. Run her a hot bath and massage her afterwards, be a gentleman and use your skills with touch to get her started.
Tactic Two is Trciky, deceptive, but powerful...
Jealousy...yes, sometimes jealousy can get a woman (or man) hot and bothered...maybe you can create a girl from work or school or something that has started giving you signals...tell your lady this "mystery" girl has been coming on to you, but you have asked her to stop because you are faithful to your lady. Every couple of days or so bring up the mystery girl and how she is tempting you with short skirts, but you refuse to give in becasue you love your lady too much. You have to work this scenario in a manner that will not make your lady doubt you, but it may stir something up for her.
Maybe she doesn't feel like sex, but she DEFINATELY will NOT want another woman offering to give you head or offering sexual intercourse. This can be tricky and is only recommended if the first tactic (touch and date nights) fails. Be prepared to lie and fabricate cards from this mystery lady that is after you maybe an ex or something.
Jealousy can be your friend in getting your lady in bed more often, but it must be used carefully and never make her feel like you would violate her trust...just make her feel your pain because you are being loyal and someone else wants you...she will probably give in...keep us posted on what you try and how it goes.
Try strawberries and cream while she is in the bath or chocolate...there are many aphrodisiacs to consider...forget shit like pharomones...this is deeper than that.
Also do NOT settle for once a week...whenever you settled for less that is when the tables turned...always push for more until you find some common ground...honestly once a week would kill me, and less than that would never be acceptable.
SF