If it is upsetting you then it is not right for you.
There are other methods of looking at sleep which don't involve going against your instincts.
Self soothing unfortunately is not a skill which can be learnt or taught - and it can't be taught by leaving him to it, he is not old enough to have the emotional regulation skills to do that. This is absolutely not a criticism of you, I understand it is so often said that children "need to learn to self soothe" and this is a very common method used to "teach" it, but what it is actually teaching is that you're not going to respond. Which is OK if that is your aim. If you have decided that you don't want to respond to these kinds of wake ups in the night any more, then it's an effective method to cement that new habit, and for most people it works within a couple of nights with minimal upset. You could perhaps look at doing it with shorter intervals and something more like pick up put down, where you completely calm him before leaving rather than a quick reassuring pat and then leaving. If it's not your aim, then maybe look at something different.
For example here are some tips from Lyndsey Hookway (you need to click through to see all the pictures) No controlled crying, but several suggestions to reduce night waking/reduce reliance on you for night waking/reduce the burden on you.
www.instagram.com/p/CHD6WHAAM5V/
I know that one thing she often suggests is adjusting naps, and that a lack of sleep pressure (the build up of the hormone adenosine) can be the cause of frequent night waking. So it may be worth looking at something like this compared to how your son was at 7 months old. However sleep can also be developmental and it is normal for there to be more disturbed sleep at around this age - sometimes called "the 9 month sleep regression" - this could be to do with separation anxiety. When was it you went back to work? Babies can also "reverse cycle" at night which is where they breastfeed more to kind of make up for being away from you in the daytime. If you think that's happening you might be able to look up techniques to change that habit, and see if that helps with the sleep.
It can help to work out what you actually want and what's realistic - it doesn't have to be all or nothing although the method you have chosen is quite an all-or-nothing one. Do you need him to sleep right through? Would a longer stretch be something that works? Would you get more sleep if he was in your bed for example (I know for many people the answer would be no!) Or is he currently coming to your bed and you want him to stay in his own? Would you like to night wean? Having a kind of "curfew" on feeds and bedsharing worked well for me and helped me feel a bit more in control without feeling like I was doing something cruel.
Good luck with whatever method you choose.