I think part of the issue here could be that you are struggling to accept how much your life has changed since you had your son.
Parenting is hard, there is no doubt about it. Parenting children who are poorly is even harder. And lack of sleep makes everything more difficult. It's totally normal not to want to give up your evening stroking your little darlings forehead until he eventually gives up and nods off.....
We give up certain freedoms and a lot of our own time when we become parents. For me, having a second child has made me realise that you really do need to do what works for you to get some of your time back and I'm much happier and more relaxed as a result. The following things may not be for everyone but have helped me:
A cleaner
Taking turns with husband to have a long lie in at the weekend to catch up on sleep.
Being structured and careful how I spend my time, I've really started to limit guests/play dates and baby group activities (with my first we did too much and it was exhausting). This has allowed me to make more time for myself and my hobbies.
Simple dinners like fish fingers for children when needed.
Skip bath time when I can't be bothered with it.
Let them watch TV or play on kindles when they are tired or when I want to get stuff done.
If they really won't sleep I'll occasionally give up trying, bring them downstairs and carry on with my evening, albeit watching kids TV...
Calpol....administer it when needed even when you don't know what it's needed for (e.g. they are exceptionally grumpy...could be in pain).
If they wake up in the night I sometimes let them in our bed and they go to sleep. Much better than staying awake all night. Get a bigger bed if you need go.
Kindle gets turned on after a bad nights sleep
I give endless somewhat healthy snacks when needed, for example when I want to keep them happy in the buggy
I also use bribery....probably a faux pas.
Crank up the tunes to drown the whinging out and and dance it out, everyone feels better for this!
Sometimes for me it's just a case of realising that they are having a bad day, I won't achieve much and that I am going to have to give up my day in order to keep them happy, then crack on with what I want/need to do later.....
Finally, do things you enjoy with them. We like arts and crafts so I get the playdoh out, set them up with colouring etc, and let them paint my well protected table! Got to try and make things fun even though they sometimes make this difficult.
And if you want to just have a cup of tea and call a friend, or do an online shop then stick them in the bath, fill it with toys and let them play whilst you sit and watch/relax.
Despite all of this it's sometimes really tough and I can't wait to get them to bed. We have fun though and I much prefer my life with them to the life I lead before and they make me laugh way more than anyone else does!!