naturalbaby I'm an old biddy and I've been there and done that. In fact am still doing it, though not to the extent it used to be. My DH was a merchant seaman, so was away for up to six months in the early part of our marriage, and four months at a time when he was promoted, etc. We have four children, and I never had any help with them (didn't want or need it), apart from my Mum occasionally babysitting. The trick is to treat it as part and parcel of life, and to look on the good side. The excitement when Daddy was coming home was something to behold!
Some women would say to me - I couldn't do it. Well, do you know something? I did it, because this is the person I love with all my heart, and I'd rather be with him that be with someone else who's there all the time, and no way would I ever have expected him to give up the job he loved. Nowadays DH is office-based and only travels out to ships for a week or so at a time on inspections, and I look on it as a wee holiday from the usual day to day stuff. In fact, I dreaded the day he started on the 9-5 thing - I knew it would come one day - although it's worked out better than I had thought.
Anyway, just mentioning the above to let you know that there are good and bad sides to what you're experiencing - you just have to try and find the good and concentrate on that.
It's a little sad that you seem to look on the SAHM stuff as a bit of a grind. Maybe I'm different, but I loved looking after my children, and I do miss them being little these days. Please try not to push him away, as that way lies grief. Look forward to him coming home, prepare a special meal, get a bottle of wine in...whatever it is that can make it that bit special.
As others have said, perhaps it'd be a good idea to pop along to your GP. It does sound as if you're a bit depressed, and if you can get out of the depression, then life will, I'm sure, improve for you, and you'll find his absences easier to bear.