OP do what is best for your circumstances and family.
I sleep trained using PUPD with a sleep consultant just before my daughter was 6 months old because she refused to nap at all from around 2 months old. She would stay awake for 12+ hours straight many days. Others, I would walk around with a pram for 2+ hours and get a 20-30min nap out of her if I was lucky. She was suffering from lack of sleep, overtired, grumpy, clingy etc. She slept fairly well at night (4 month regression aside) so me resorting to sleep training didn't have anything to do with my lack of sleep. I tried every single thing all the self-righteous co-sleeping attachment parents have suggested - not one of them worked. However, once she started sleeping, life changed for all of us. I had a happy baby all day who was a delight to look after. Her growth accelerated massively too. Lapin hit the nail on the head when she said most cry anyway when they are overtired.
Sleep is still hard work for us in that she only sleeps well in her cot in a dark room with absolutely no stimulation and white noise on. She unfortunately is unlikely to ever be one of those babies that will fall asleep when out and about in the pushchair/car seat because she is tired - she will still stretch herself to stay awake because she is so alert. I've accepted that and my life revolves around her naps as I know I have a happy baby that way.
As a HCP who specialises in paediatrics, I did a lot of research into sleep training (including asking specialists at a leading paediatric hospital) and it's long term effects before starting. There is absolutely no evidence of harm when sleep training. It is still highly encouraged by specialists in many circumstances (and I'm referring to paediatric consultants here with 10+ years training and experience) because of the harm sleep deprivation causes to a child's developing brain.
Be consistent with whatever you do (which you certainly are doing now) and you will get there. If you feel like it may be falling apart, speak to a sleep consultant rather than people on here. Most have best of intentions but multiple opinions confuse the matter even more.
Those on this thread who co-sleep seem to struggle with the basic concept of every child being different. I would happily have also co-slept in those early days for nights and naps if she had settled but she didn't want to sleep that way. Her need for sleep trumped everything else so we had to find an alternate way.