OK, gotta reply because this has been the number 1 problem in my sex life, too.
I assume, before I fully respond, that you do not have a history of rejecting his advances. If you do - that would speak volumes about why he no longer wants to initiate. If you don't - here is my advice:
First thing - don't assume he should know you are in the mood. I can walk up to my husband naked with a condom in my hand and he still wouldn't get it. Seriously. Men can be dense (no offense intended). I spent a couple of years playing a game where I thought I was being plainly obvious that he could take me at any time, and he just didn't see my signals. So many years wasted! Speak to him plainly and clearly at a time when you are in a non-sexual situation about this. I sat my husband down at the dinner table one day (sans kids) and just told him - I would like to have sex this many times a week, this is what I have been doing to try to get your attention, what would be a better way for me to get you to understand I'm ready to go?
Second thing - is your husband an assertive guy in other areas of his life? My husband is not. He's not lazy, but he is shy and even though I am his wife and he should be comfortable around me, he still has a hard time initiating and being assertive and taking charge with me. I had a frank discussion with him and told him I would like to see more assertiveness from him. I said it in a non-confrontational manner, basically said - it would really turn me on if you would initiate things with me more often, I want to see that you are in the mood and thinking about me. My husband and I both talk openly about masturbating and we both know the other does it, and I know he has a tendency to assume that if I don't go after him myself, I must not be ready to go. So instead of coming to ask me he will just take care of himself. I asked him to stop doing that and to always ask me first. He has taken my request seriously - but beware! If you get him to come to you first, you may have no idea how much of a sex drive he really has. I have found that I have seriously underestimated the amount my husband must have been masturbating because he is coming to me 2-3 times a day at times! I work hard not to turn him down (I want to make sure I reward him for being so forward with me like I asked him to!) but yea...I am exhausted LOL. It's a good exhausted though.
Third thing....ask him if there is anything new he would like to try in the bedroom. Do you think your sex life may be stale or boring? What kind of porn is he looking at, is there something you think he might be wanting to try that you've shyed away from in the past? I would make an emphasis to him that you are open minded (with certain limitations...whatever they are), that you want to please him, that it turns you on to please him, and that you want to make him excited about your sex life. Make sure he understands your enthusiasm.
If you can have an open discussion with him, it should help things. Make sure you frame the discussion in terms of "It would really turn me on if you did _____." instead of questioning "Why are you always looking at porn? Why don't you initiate more often?" My husband will clam up if it seems like I am finger-pointing.