First, you should not feel as though this problem is yours alone because intimate relations are the right and responsibility of both the husband and the wife. Given societal awkwardness towards discussing such sensitive matters, it is simply beautiful to know that the Prophet Muhammad sal allahu alayhi wasallam, who epitomized shyness throughout his life, taught us:

"As narrated by Uqba bin Amir radhi Allahu anhu, "from among all the conditions which you have to fulfill, the conditions which make it legal for you to have sexual relations (i.e. the marriage contract) have the greatest right to be fulfilled."  Bukhari 50 #882).

Both husbands and wives are therefore called to account by Allah subhanahu wa T'ala for the extent to which they willingly and enthusiastically strive to satisfy each other’s desires in a manner pleasing to Allah Most High. The Qur’an reminds both husbands and wives that they may exercise considerable creativity in pleasing one another, of course within the bounds set by Allah Most High. On the  prohibition of sexual relations between spouses during menstruation, in which Allah Most High states:

"And they ask you about menstruation. Say: It is a discomfort; therefore keep aloof from the women during the menstrual discharge and do not go near them until they have become clean; then when they have cleansed themselves, go in to them as Allah has commanded you; surely Allah loves those who turn much (to Him), and He loves those who purify themselves" (Al-Baqarah 2: 222).

Second, we urge you to sit down with your husband and to talk to him in a very calm, rational manner about your feelings in this area. Encourage him to explain to you why he is not as inclined to have intimate relations with you. Is it that he is too tired? Is it that he does not find you appealing? If he is not as forthcoming or he tells you that in fact it is not that he is tired or that you are not attractive, then keep your radar on for other warning signs. It is possible that he has reached a point in his life whereby he is just not as interested in intimate relations. You need to try to help your husband understand that you are personally being affected in very negative ways by not being able to have intimate relations with him more often. Offer practical help such as:

Going out without the children 

Spending time together at home, alone after the kids have gone to sleep. 

As you said, your husband does respond when you push the issue but then somehow, the excitement phases out and you are back to sporadic intimate relations. Be sure to remind him while he is responsive of just how much you appreciate him!

Finally, every chance you get, let him know how much you love him and how much you desire to be with him. Remind him how grateful you are to him when you do have relations because you find him irresistible. If you are thinking this is not true, why should I say something which is not true, then think again. There is no harm in exaggerating in this area, if by doing so, you are helping your husband to feel more motivated in sha ’Allah to attend to your needs. Be romantic, be creative and do not give up on him or the marriage. In sha ’Allah, in time, with your efforts and the guidance and assistance from Allah Most High, your husband will come to his senses and find out what he has been missing all this time.

And Allah knows best.

For your further guidance, please try the following links:
•   Romancing the Stone
•   After the Wedding