Happy that you wanted to plan your pregnancy perfectly.
The tests you may do before planning pregnancy:
Hemogram,
Fasting
sugar
Viral screen ( Tridot, HBsAg)
Urinalysis
Ser.
TSH
Ser.
CreatinineVitamin B12,
Vitamin D
Rubella, varicella titres
Genetic screening for some diseases, if prone
Ultrasound pelvis
PAP smear
Next Steps
Start taking Folic acid supplements, other supplements depending on the test result.
A good natural protein supplement may prove useful in addition to balanced nutrition for a healthy weight gain
Health Tips
Good to get a general body examination from a doctor, it will give a hint in which way you should be investigated
Some other tests also may be necessary depending on your previous history