Is an 8kg weight gain at 26 weeks ok? i started at 62 kg

That is little too: excessive. however from the start of pregnancy till 26 weeks it is possible. make sure you do not have swelling of feet and that your BP is ok. also your doctor needs to check if your baby is not too large for dates etc. Rapid weight gain occurs more so in the third trimester

Yes: It sounds like you are on track with normal weight gain. However, weight gain is less important than fetal growth and weight gain. The better question to ask your OB provider is, "Are my fundal heights appropriate and did my US show adequate growth?" There seems to be an obsession with weight gain in pregnancy and honestly many women gain too much. Keep up a healthy diet and congrats.