I left my followers in Novak. I do have mods that let me have more followers than the vanilla game allows.
Here are my Mods:
FalloutNV.esm
DeadMoney.esm
HonestHearts.esm
OldWorldBlues.esm
LonesomeRoad.esm
Community Bugfix Compilation Patch.esm
CBC Dead Money Patch.esm
Ambient Temperature.esm
Moddable Unique Weps.esm
wsix.esm
ELECTRO-CITY - CompletedWorkorders.esm
ELECTRO-CITY - Highways and Byways.esm
DeadMoneyWeaponFixes.esp
McCarranFixes.esp
Vault11HouseFix.esp
Vault34Fix.esp
WeAllGoTogether.esp
AutoSaverNV.esp
CASM.esp
HUD Extended - Ambient Temperature.esp
IIWR 2.0.7.esp
brotherhoodweaponstash.esp
ProjectPrimm.esp
NewVegasStrip&FreesideMarkers_v2.esp
PerkEveryLevel.esp
XFO - 6aa - Epic Skills - Effects Over 100 (NVSE req).esp
wsixInnuendoNPCs.esp
mysterious increase.esp
Clanf_NoWeaponsRemove.esp
hold_breath.esp
mojave music radio expanded v1.1.esp
Rustyhwys.esp
weight50000.esp
Assault Carbine mods.esp
Better Binoculars High.esp
c4nuke.esp
EnergyWeaponDeNerf.esp
HHWeapsInNV.esp
HHWeapsInNVNPC.esp
PlasmaRifleAwesomefied.esp
ZLArmaments.esp
ClassicPowerArmorPulseRifle.esp
CombatArmor_MarkII.esp
CRHDV3O2.esp
Desert Recon Kit.esp
NCR Black Ops Stealth Armor.esp
RCSS.esp
RepairLists.esp
Essentialplustweaks.esp
ICC.esp
Max Followers 12.esp
UnlimitedCompanions.esp
levelcap45.esp
Brighter PipBoy.esp
dD - Enhanced Blood Main NV.esp
dD-No Screen Blood.esp
Dead Money - No Collar Explosion and No Poison Cloud.esp
fastervats.esp
ImprovedImplantRegen.esp
MusicRecovery.esp
NoDegradation.esp
No Weapon Remove Dead Money.esp
Vault_34_better_reactor.esp
XtraSpecialNV.esp
WeaponModsixpanded.esp
Vurt's WFO.esp
URWLNV.esp
Western Sky.esp
ELECTRO-CITY - Darker Nights.esp
Interior Lighting Overhaul-Realistic Interiors-Full.esp
ILO-RI-Dead Money.esp
Depth of View IE Gentler.esp
Chinese Stealth Armor Patched.esp
HonestHeartsCheats.esp
Merged Patch.esp

Total active plugins: 75
Total plugins: 83

The first thing is to shut off you mods. Whenever a new DLC comes out the mods are not necessarily going to be compatible, so that's the first thing to eliminate from the equation.

the game says that i still have followers, that i must go alone. But i left the 4 followers that are with me in Novak and asked them to wait.

you need to tell them to go to luky 38

just did that TY, I can't wait to have some mods that lets me bring my followers. LOL

Try using one of the companion dismissal terminals. That will ensure all your companions properly fired.
Companions must be sent home or to the lucky 38. Telling them to wait mode doesn't count.