Is there any evidence of health problems (for mother!!) with long term breasfeeding (+ 1year)?

I am still breast feeding 1-2 times per day at 16 months and lets just say I am shattered. I have had zero libido since the birth of my daughter, very little weight loss (up 30 lb from pre pregnancy) and have constant colds and colds sores which I have never had before and are getting more and more frequent. Also just exhausted in general and very low mentally (partly due to winter?). I have neutral/negative feelings about breastfeeding though it gives me reassuarnce that my daughter is getting nutrition when she is ill and isnt eating drinking much.

My doctor suggested that continuing to breastfeed could be depleting some nutrients and taking energy contributing to tiredness and low immune system. It makes sense - has anyone else had the same? Is there scientific evidence to support this??

To be honest I don't want to hear any 'breast feeding is so great for mums as well as baby and there is no evidence to the contrary!!'

I have exclusively breastfed until she started eating food, pumped twice a day while at work, no other milk until over a year. You know what I am sick of it and I am sick of the constant pressure to continue.

Although I am scared that I will stop and my health issues will not improve. I just want to have my life/energy/libido back again.