That sounds very like my first born. She didn't have a diagnosis of reflux at the time but she was super tense and panicky and miserable all the time. We'd had some problems establishing breastfeeding at first as she had strong tongue and lip ties so feeding took forever. It felt like she spent most of her time just crying or feeding and I was just spending all my time staring at her ear as she fed or looking at her eyes squeezed shut in a red, angry crying face. Then in the rare windows where she was awake and calm she would never make eye contact with me, always turn her head to the side and definitely nothing approaching a smile until 8 weeks. I felt so sad and was desperate to feel this rush of love and connection that all my nct friends had talked about. I looked at their babies staring into their mummies' eyes and all the smiling and joy and it just made me feel like there was something very wrong with either my parenting or my new daughter.
Fast forward 2.5 years and she is the brightest, happiest little girl and spends all day smiling and giggling (in between normal 2 yr old tantrums) and makes loads of eye contact while she is talking to me. She is still massively sensitive to things like loud sudden noises and very risk averse, and has a full body jumping/trembling reaction when she is frightened (which is often). I've just put it down to the fact that she is very very sensitive. But she is also incredibly smart and just plain different from the loud rough and tumble toddlers. She has great fun with her friends, is popular and sociable at her nursery and although generally shy and introverted, she is very normal and happy and smart.
Looking back I wish I had worried less about thinking something was wrong. I also wish I'd understood more about newborn's need to sleep. All those times she was avoiding meeting my gaze (and I was feeling sh*t and panicking) and she was probably just exhausted. Even 45 mins awake is a long time for an under 12 week old - especially if they are sensitive and easily overstimulated.
I wish I'd spent more time just feeding her to sleep, letting her sleep upright on my chest and just hold her and try to keep things calm. Instead I wanted to do everything right and give her the right stimulation, and not make a rod for my back (I bloomin hate any advice that comes with that line).
A wise older mum I knew, maybe she could see I was struggling, told me about her post natal depression and how she was so glad she'd always held her infant in a stretchy wrap sling as she knew that their two hearts had been close together even when mentally she'd been struggling to feel the bond. I never would have called what I had at the time PND - more just lots of stress and worry and sleep deprivation and hormones. But that probably is a big element of PND too.
Her advice which I'm forever grateful for was to wear the baby as much as possible, kiss her and sniff her head loads, let her sleep on her tummy upright on my chest for as long as she wanted during the day, and assume that whenever she cried she needed to feed or sleep or both. Basically just let everything else go as long as you can get outside for a walk every day. So I followed that and slowly things got easier and I felt more and more connected to her. She was a whole lot happier when she was pain free with a full tummy and sleeping most of the time. I slowed things right down, changed and bathed her less, had shorter shopping or cafe date sessions, basically just cocooned the two of us. And slowly came out of it all at 12-16 weeks when everything had started to fall into place and get MASSIVELY easier.
Yes she was "late" to smile and avoided eye contact whenever she was tired - still does if she is concentrating hard on something or feeling overwhelmed/shy. But she is absolutely developmentally normal and socially fine and now. I'm so glad that I did the things that I could (holding, wearing, smelling, stroking her lots, thinking about our hearts being close and what she could hear) as those are the things that made the bond establish. Then later, when she was happier and well rested she would look into my eyes and smile, my heart near enough exploded.
Give it time and slow things down. I'm sure it will happen for you too x